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DA1855A Differential Amplifier Operator`s Manual

1. When using readout encoded probes which the DA1855A senses the PVG readout calculates the effective differential offset at the probe tip Of course both probes must have the same attenuation factor In the Vcomp Mode the maximum OFFSET VOLTAGE input is limited by the DA1855A common mode dynamic range In the Vor mode it is limited by the dynamic range of the internal Vpirp amplifier 18 Operator s Manual Table 2 and Table 3 will help the operator stay within the maximum input voltage limits and understand the relationship between the actual voltage applied and the effective voltage Effective voltage is always referred to the input of the DA1855A or the probe tip if a probe is used When using probes the maximum effective voltage range may be limited by the maximum voltage rating of the probe Table 2 Effective Offset Range with 11 Probe Front Panel Effective Offset Settings Range Attenuation Vcomp x1 1 15 5V 10V x1 10 155 V 100V X10 1 15 5V 1V x10 10 155 V 10V NOTE The effective voltage is always increased by the attenuator It therefore follows that any probe will increase the effective voltage of both Vcomp and Vor by its attenuation factor For example a probe with a 100X attenuation factor will increase the effective full scale range by 100 Table 3 Effective Offset Range with 100 Probe Front Panel Effective Offset Settings Range with 100 Probe
2. The input is not disconnected when the ATTENUATOR is set to 10 The input attenuator can withstand up to 200 Volt continuous input Rear Panel Power Normal instrument operation is obtained with the power switch in the 1 ON position The instrument can be used immediately however it requires a 30 minute warm up period to reach specified performance Prior to reaching operating temperature the amplifier offset will drift and the output from the Precision Voltage Generator may not be within specification In high humidity environments the time to stabilize may be much longer In high humidity environments or when warm up time inhibits power switch left in the 1 ON position Power Up Indicator Upon turn on the model number and firmware version are briefly displayed in the PVG readout For example 1855 12 indicates that the instrument is a model DA1855A and the firmware version is 1 2 17 DA1855A Differential Amplifier Precision Voltage Generator Offset Voltage The rear panel OFFSET VOLTAGE BNC PVG output connector is a monitor of the Precision Voltage Generator PVG The voltage present on this connector is the same voltage as that applied to the INPUT when the INPUT coupling is set to VCOMP or internally to the DA1855A when VDIFF is selected The OFFSET VOLTAGE output can be used to monitor the PVG with a digital Voltmeter DVM A low pass filter between the PVG output and the INPUT removes radio frequency interfer
3. OFF DC In OFF mode the input connector is disconnected from the amplifier input and the amplifier input is connected to ground The AC coupling capacitor is connected between the INPUT and ground through 1 MOQ resistor independent of the INPUT RESISTANCE setting In this mode the AC coupling capacitor is quickly charged to the average DC input voltage OFF mode is also referred to as precharge mode Precharge is particularly useful prior to selecting AC coupling when the input voltage has a DC component in excess of 19 V The DA1855A input coupling is set to OFF and connected to the circuit under test When the INPUT is changed from OFF to AC mode the coupling capacitor is already charged and the trace properly centered on the oscilloscope screen Additionally the risk of tripping the input overload detector and automatically disconnecting the input is eliminated In the AC mode the INPUT is connected through an AC coupling capacitor to the amplifier input or the input attenuator The coupling capacitor retains its charge when the input is switched to DC making it possible to return to the same circuit without the precharge time But this also makes it possible to discharge the coupling capacitor into another circuit under test if its DC voltage differs by more than approximately 19 V from the voltage on the coupling capacitor NOTE The discharge current from the AC coupling capacitor is limited to about 70 mA In some situations th
4. ITT Pomona 3285 BNC adapter Female to female AIM 25 7430 ITT Pomona 3283 Banana Plug adapter BNC female to dual banana plug ITT Pomona 1269 57 DA1855A Differential Amplifier Preliminary Procedure 1 Connect the DA1855A Differential Amplifier to an AC power source within the range listed in the Nominal Characteristics in the Specification section 2 Allow at least 20 minutes warm up time for the DA1855A and test equipment before performing the Verification Procedure 3 Turn onthe other test equipment and allow these to warm up for the time recommended by the manufacturer 4 While the instruments are reaching operating temperature make a photocopy of the Performance Verification test record located at the end of this section and fill in the necessary data The warranted characteristics of the DA1855A Differential Amplifiers are valid at any temperature within the Environmental Characteristics listed in Specifications However some of the other test equipment used to verify the performance may have environmental limitations required to meet the accuracy requirements needed for the procedure Be sure that the ambient conditions meet the requirements of all the test instruments used in the procedure NOTE When the oscilloscope input is connected to the DA1855A AMPLIFIER OUTPUT the oscilloscope input impedance must be set to DC 50A unless otherwise stated Use a 504 inline termination when using an
5. s attenuation factor Two probes with a 1 accuracy specification can yield a CMRR as low as 50 to 1 at DC while the amplifier CMRR may be higher than 100 000 to 1 At high frequencies the CMRR will be worse A differential probe pair must allow for matching at DC as well as over their useful frequency range Changing the compensation of a differentially matched probe set without following the proper 22 Operator s Manual compensation procedure can result in a significant decrease in the CMRR capability of any differential probe pair It is a good practice to compensate a probe pair for a given amplifier and then leave the probe pair and amplifier together as a system Similarly it is important that once compensated for given amplifier each probe always be used on the same input one probe always on the INPUT and the other always on the INPUT DXC100A Differential Probe Pair The DXC100A is a high performance matched passive differential probe pair designed for use with Teledyne LeCroy DA1855A series differential amplifiers The probe pair consists of two well matched individual probes that share a common compensation box to allow the attenuation factor on both probes to be simultaneously switched between 10 and 100 When used with the DA1855A Differential Amplifier the probe s attenuation factor is automatically incorporated into the effective gain display and the decimal properly located in the Precision Voltage Generator
6. 73 DA1855A Differential Amplifier k Set the oscilloscope to display channel 1 coupling to DC and impedance to 50 Q and the vertical sensitivity as necessary to measure the amplitude of the displayed waveform Refer to Figure 21 Oscilloscope DA1855A pasos ee a ono Sonn np Amplifier Output 4 Set Input to DC 500 6 BNC Cables BNC Y Leveled Sine Wave Generator Frequency Reference Output aa a O Ges Female o EIS EI BNC Adapter g OO Output Figure 21 LF CMRR Check Setup The displayed signal is the Common Mode Feedthrough Use the oscilloscope ZOOM function and averaging if needed to increase the size of the displayed waveform and to reduce noise NOTE This measurement needs to be made very carefully The signal is only several hundred uV in amplitude and measuring the peak to peak amplitude of this signal using oscilloscope measurement functions may cause erroneous reading Measure only the amplitude of the common mode feedthrough not the total value of the signal plus noise m Record the displayed Common Mode Feedthrough at 70 Hz to two digit resolution in the Test Record n Calculate the Common Mode Gain by dividing the Common Mode Feedthrough in UV by 20 000 000 uV Record the result to two significant places as Common Mode Gain at70 Hz in the Test Record Keep all of the leading zeros or use scientific notation o Ca
7. A low frequency compensation made with the entire waveform visible on screen is usually adequate for most measurements However when a signal s amplitude is greatly magnified as can be the case when using a differential amplifier a small error in the low frequency compensation flatness can cause major error in voltage measurements especially when measuring saturation voltages Figure 4 through Figure 7 illustrate how this seemingly minor adjustment can make the saturation voltage s DC level appear to be incorrect A voltage probe appears to be properly compensated on a 400 V square wave when viewed at 100V div 100 Vidiv 0 1 msec div Figure 4 41 DA1855A Differential Amplifier When viewed at 500 m div the same 400 V square wave shows the probe compensation to be slightly over peaked B H 500 mV div 0 1 msec div Figure 5 When the time div is decreased to value normally used to view 20 to 150 kHz switch mode power conversion circuits the slightly peaked LF compensation appears as a DC level shift Figure 6 Viewing a power FET s saturation voltage with the slightly peaked LF compensation makes the voltage appear to go negative In this example the repetition rate of the power supply is 60 kHz 42 Operator s Manual T 200 mV div 0 5 usec div F
8. Attenuation Vcomp VDIFF x1 1 1 55 kV 1kV X1 10 15 5 kV 10 kV X10 1 1 55 kV 100 V x10 10 15 5 kV 1kV Although the full scale range may be 10 kV or 15 5 kV most probes have a much lower maximum input voltage rating which must not be exceeded Amplifier Output The AMPLIFIER OUTPUT BNC is intended to be used with an oscilloscope spectrum analyzer or instrument having a 50 Q input resistance The amplifier s output impedance is 50 Q Without the 50 Q load the amplifier gain will be uncalibrated and will be approximately twice the amount indicated on the front panel Proper operation of the 1 MHz or 20 MHz bandwidth limit filters requires an output load impedance of 50 Q 19 DA1855A Differential Amplifier Remote Operation A REMOTE connector on the rear panel of the DA1855A allows total control of the instrument through a Teledyne LeCroy oscilloscope when connected to ProBus using the supplied cable All of the instrument functions can be controlled through the oscilloscope user interface Remote control is also possible using commands sent through the IEEE 488 bus or through RS 232 connected to the oscilloscope The DA1855A cannot be remotely controlled without a Teledyne LeCroy oscilloscope See page 46 for a description of the Remote Commands When the ProBus cable is installed the buttons on the front panel of the differential amplifier are disabled NOTE Remote operation requires software vers
9. Connect the terminated end of the termination attenuator BNC Tee combination to the DA1855A INPUT Connect the DMM to the free female end of the BNC Tee connector using the previously removed cable 63 DA1855A Differential Amplifier Sine Wave Generator DA1855A Ol i m DD B HHH maran eeieeeiellskz Output a BNC to Dual Banana Plug Standard 10 Attenuator Adaptor 500 Attenuator BNC Tee Figure 12 X10 Gain Accuracy Setup p Adjust the sine wave generator output amplitude to read200 mVrms 50 mV on the DMM q Record the DMM reading to 100 uV resolution as Sine Wave Generator Output Voltage in the Test Record r Disconnect the DMM cable from the BNC Tee and remove the BNC to banana plug adapter from the cable and DMM s Connect the DMM cable to the DA1855A AMPLIFIER OUTPUT connector t Insert the precision 50 Q termination between the other end of this cable and the input of the DMM See Figure 13 u Set the DA1855A GAIN to X10 64 Operator s Manual DA1855A Sine Wave Generator Front Rear Se ooooog QO o Cen o DI DED 8 e er DoD oOngD goo HDD a Output Precision 500 Terminator Standard 500 Attenuator 10 Attenuator S DMM E Bsleisleieiel OO 198 Figure 13 X10 Gain Accuracy Setup BNC Tee Divide the sine wave generator output voltage recorded in step 2 q by the exact attenuation factor recorded in step 2 I
10. PVG display Probe Grounding The DXC100A Probe Pair is supplied with accessories that allow for three methods of connecting probe grounds In most cases when the common mode portion of the signal consists mainly of low frequencies 1 MHz and below the probe ground leads should not be connected to the ground of the circuit under test They should be connected to each other This minimizes the effects of ground loop currents The signal corruption caused by not having the probes connected to the ground of the circuit under test will be common to both inputs and will be rejected by the differential amplifier However when working in an environment with high RF ambient noise it is best to connect the probe ground leads to a good RF ground near the point where the signal is being measured The best way to determine which probe grounding technique should be used is to try both methods and use the one that gives the least corruption of the differential signal When adjusting the compensation and probe CMRR the use of probe tip to BNC adapters is required They provide the best performance of the three grounding method 23 DA1855A Differential Amplifier General Operating Information This section will help you become familiar with the operation of the DA1855A and how it interfaces with an oscilloscope To carry out the following exercises you will need an oscilloscope and a general purpose function generator Power Connection Ch
11. lt 1 X10 gain Accuracy 2 9 Sine Wave Generator Output Voltage 2 j Attenuator Output Voltage 2 l Exact Attenuation 2 q Sine Wave Generator Output Voltage 2 v Amplifier Input Voltage 2 w Expected Amplifier Output Voltage E Measured Amplifier Output Voltage 2 z X10 Gain Error Test limit lt 1 10 Attenuator Accuracy 3 f Sine Wave Generator Output Voltage 3 g Expected Output Voltage 3 m Measured Amplifier Output Voltage 3 0 10 Attenuation Error Test limit lt 1 0 X1 Bandwidth and Calculated Rise Time Measured 3 dB Frequency at X1 Gain on Test limit gt 50 MHz Calculated Rise Time at X1Gain KE Test limit lt 7 nsec 78 Intermediate data Test Result K K MHz nsec High Frequency CMRR Step Description Intermediate data 5 e Amplifier Output Voltage at 10 MHz V D Differential Mode Gain at 10 MHz 5 w Common Mode Feedthrough at 10 MHz 5 Common Mode Gain at y 10 MHz 5 aa Common Mode Rejection Ratio at 10 MHz Test limit 1000 1 Low Frequency CMRR 6 m Common Mode Feedthrough at 70 Hz V 6 n Common Mode Gain at 70 Hz 6 0 Common Mode Rejection Ratio at 70 Hz Test limit 50 000 1 6 x Common Mode Feedthrough at 100 kHz V 6 Common Mode Gain at v y 100 kHz 6 z Common Mode Rejection Ratio at 100 KHz Test limit 2 50 000 1 Precision Voltage Generator Accuracy 7 C PVG Zero Output Voltage Test limit 0 05 of reading 500 uV 7 9 PVG Output Voltage at 15 5
12. 1 ATTENUATOR button on non ProBus operated systems or selecting Atten in the List Select menu and setting the attenuation to 1 in systems with ProBus interface The waveform s magnitude on the oscilloscope s display will increase by a factor of 10 and extend off the top and bottom of the screen The X1 light will be lighted in the EFFECTIVE GAIN display Reduce the function generator s output until the oscilloscope s display is again 2 divisions peak to peak The overall sensitivity of the DA1855A and the oscilloscope is now 50 mV div Now press the X10 GAIN button Observe the following changes The INPUT s DC light will momentarily go out and its OFF light will be lighted before returning to their previous states This momentary change is the result of the DA1855A automatically adjusting its DC Balance The X10 light will be lighted in the EFFECTIVE GAIN display and the display on the oscilloscope will again extend off screen The overall sensitivity of the DA1855A and the oscilloscope is now 5 mV div Comparison Voltage Operation Vcomp Leave the DA1855A set up as in the previous exercise or set as follows INPUT DC INPUT OFF BW LIMIT FULL GAIN X10 ATTENUATOR 1 INPUT RESISTANCE 1MQ PVG 00 00 COMPARISON or COMPARISON DIFFERENTIAL EFFECTIVE GAIN X10 Set the Function generator s output to 50 kHz and 100 mVp p sine wave and the output connected to the DA1855 s INPUT Set the oscilloscope to 50 mV div equivalent
13. 4 Warranted Characteristics ccccccccsecceceeeeeesenceeeeeneeeseneeeeeseaeeeeesaeeecceeeeeeseneeeesseneeeeseeeees 6 Typical Characteristics ccceeecceeseeceneeseneeeeeeseeeeseaeeeeeeseaeeeaeeseaeeeaeeseaeessaeeseaeeeseeeseeeenates 7 Physical Characteristics ccccccceceseeceeeeeeneeseeeeeeeeeseeeeeeeeseaeeesaeeseaeeeeeeseeeeeneeesieeseneeeeeeeeeaes 8 Uer 9 Model DeSGription ii eneee an ere ia aa eieiei 10 Rack Mount Versions sisciececcicesscesenscncsndevecuedetpeneedsandeniendeanndanecaesnesdnadicdeaedsaneedvannlcadednaente 10 Power Cable Otion 10 ele Ei Wee TEE 10 Optional ACCESSOLICS 0 eeeceeesceceneeeeeceseaeeeeaeeseeeteceseseeeseceseaeeeeaeeseaeeeeaeeseseesnaeeseseeeneetaes 11 OPC AON WE 11 General MPOMALON seisce spaa iaey ceaenveses savage cod R E EEEa 11 Bulle le E 11 Etoile Eeer eege EE 12 PREAMP AMG css esscceedsecstevsnccecaczessatecec tec E E E E igure EE Eea eaae eaer 17 Instrument SettingS AAA 20 General Operating Information ccccssccescsseecsseessseeseseeenseesnseesnseeseeeeesseesseeessseeseeeeeeseesaseess 24 ower COMMECHON sssrini eieae e deed GEESS deel geeeeggee beid 24 Comparator MOG seridir enei dc estes a aaa ea EA N eanan ania 24 Differential Mode irri eaea e E ee ale ee ee 24 Setting Up the Oscilloscope with ProBus Interface 25 Setting up the Oscilloscope without ProBus Interface 30 Determining the Proper Offset Mode ceccceseeeeeseeeseeeeeneeeeeeeeeeeeseaeeeeeese
14. 7 GHz EN 61000 4 4 A1 2010 Electrical Fast Transient Burst 1 kV on power supply lines 0 5 kV on I O signal data and control lines EN 61000 4 5 2006 Power Line Surge 1 kV AC Mains L N L PE N PE 4 EN 61000 4 6 2009 RF Conducted Electromagnetic Field 3 Vrms 0 15 MHz 80 MHz EN 61000 4 11 2004 Mains Dips and Interruptions 0 1 cycle 70 25 cycles 0 250 cycles 1 To ensure compliance with all applicable EMC standards high quality shielded interface cables should be used 2 Emissions which exceed the levels required by this standard may occur when the oscilloscope is connected to a test object 3 This product is intended for use in nonresidential areas only Use in residential areas may cause electromagnetic interference 4 Meets Performance Criteria B limits of the respective standard during the disturbance product undergoes a temporary degradation or loss of function or performance which is self recoverable 5 Performance Criteria C applied for 70 25 cycle voltage dips and 0 250 cycle voltage interruption test levels per EN61000 4 11 European Contact Teledyne LeCroy Europe GmbH Im Breitspiel 11c D 69126 Heidelberg Germany Tel 49 6221 82700 82 Operator s Manual AUSTRALIA amp NEW ZEALAND DECLARATION OF CONFORMITY EMC Amplifier complies with the EMC provision of the Radio Communications Act per the following standards in accordance with requirements imposed by Australian Communication a
15. Amplifier into 50 Q DOES NOT APPLY WHEN USING A TELEDYNE LECROY OSCILLOSCOPE WITH PROBUS INTERFACE All the signals displayed on my oscilloscope seem to be twice as large as they should be This comment results from not having the output of the DA1855A properly terminated into 50 Q When interfaced using ProBus to a Teledyne LeCroy oscilloscope you do not need to be concerned about the termination resistance as the oscilloscope sets the termination mode automatically The DA1855A output impedance is 50 Q The cable connecting the DA1855A to the oscilloscope or spectrum analyzer should be 50 Q and be terminated with a 50 load If the termination at the end of the connecting coaxial cable is missing the amplifier will not be properly terminated In addition to the error in scale factor operating the DA1855Awith the output unterminated may result in poor high frequency linearity and transient response Proper operation of the 1 MHz and 20 MHz bandwidth limit filters also require 50 Q termination Poor Overdrive Recovery The DA1855A output is limited at 500 mVp p to prevent the amplifier from being overdriven by large inputs Poor recovery may still occur when the oscilloscope vertical scale is set to too high a sensitivity causing the oscilloscope to be overdriven rather than the DA1855A amplifier Care must be taken to set the vertical sensitivity such that the oscilloscope is not being overdriven 37 DA1855A Differential Amplifi
16. Description Command Syntax Query Syntax Response Format Example 48 PRx BANDWIDTH_LIMIT PRx BWL Command Query The PRx BWL command sets the upper HF 3 dB bandwidth limits of the DA1855A The arguments are in Hertz The PRx BWL query returns the upper bandwidth limit setting for the differential amplifier connected to the specified channel lt channel gt BWL lt upper bandwidth gt lt channel gt PRI1 PR2 PR3 PR4 lt upper bandwidth gt FULL 100K 1M or 20M lt channel gt BWL lt channel gt BWL lt upper bandwidth gt The following command sets the upper bandwidth of the DA1855A connected to channel 1 to 100 kHz CMDS PR1 BWL 100K CALL IBWRT SCOPE CMDS Operator s Manual Coupling PRx COUPLING PRx CPL Command query Description The PRx COUPLING command sets the input coupling for the and inputs of the differential amplifier The valid arguments are AC Ground and DC The PRx COUPLING query returns the input coupling setting of the and inputs of the differential amplifier connected to the specified channel The input coupling is ignored when PVG Mode is set to Vcomp Likewise the input coupling argument is not returned from a query when PVG Mode is set to Vcomp Command Syntax lt channel gt CouPLing lt coupling gt lt coupling lt channel gt PR1 PR2 PR3 PR4 lt coupling gt AC DC o
17. The instrument also has internal fan control circuitry that regulates the fan speed based on the ambient temperature This is performed automatically after start up Cleaning Clean only the exterior of the amplfier using a damp soft cloth Do not use harsh chemicals or abrasive elements Under no circumstances submerge the instrument or allow moisture to penetrate it Avoid electric shock by unplugging the power cord from the AC outlet before cleaning A CAUTION Do not attempt to clean internal parts Refer to qualified service personnel Operator s Manual Calibration The amplifier is calibrated at the factory prior to being shipped The recommended calibration interval is one year Calibration should be performed by qualified personnel only Schedule an annual factory calibration as part of your regular maintenance Extended warranty calibration and upgrade plans are available for purchase Contact your Teledyne LeCroy sales representative or customersupport teledynelecroy com to purchase a service plan Power AC Power Source 100 to 240 VAC 10 at 50 60 Hz 10 Manual voltage selection is not required because the instrument automatically adapts to line voltage Power Consumption DA1855A 28 Watts 39 VA DA1855A PR2 56 Watts 78 VA Power and Ground Connections The amplifier is provided with a 10A 250V 18AWG rated grounded cord set containing a molded three terminal polarized plug and a standard IEC320 Type
18. V 10 Attenuator 155 V Differential Offset Range Vor mode referred to input X10 Gain 1 Attenuator 1 V X1 Gain 1 Attenuator 10 V X10 Gain 10 Attenuator 10 V X1 Gain 10 Attenuator 100 V Comparison Offset Range Vcomp mode referred to input 1 Attenuator 15 5 V 10 Attenuator 155 V 1 Voltages are referred to the amplifier input connector Multiply by probe attenuation factor to obtain value referred to probe input e g 50 mV becomes 0 5 V at the probe tip when using a 10probe DA1855A Differential Amplifier Precision Voltage Generator Output Range Output Impedance Resolution Control Reference Type Output Routing Power Requirements Line Voltage Range Line frequency Range Warranted Characteristics 15 5V 100 100 pV Individual increment and decrement digits carry over to the next decade Oven stabilized buried zener diode Can be applied to Input and available at rear panel BNC connector 90 264 VAC 45 66 Hz Warranted characteristics describe parameters which have guaranteed performance Unless otherwise noted tests are provided on page 60 Performance Verification for all warranted specifications Gain Accuracy Bandwidth 3 dB x1 Gain Rise Time Common Mode Rejection 70 Hz 100 kHz 10 MHz Precision Voltage Generator 1 uncertainty of termination resistance gt 100 MHz lt 3 5 nsec Calculated from bandwidth x1 or x10 1 attenuation 250 000 1
19. V Test limit 0 05 of reading 500 uV 7 j PVG Output Voltage at 15 5 V Test limit 0 05 of reading 500 uV Operator s Manual Test Result 79 DA1855A Differential Amplifier Reference Differential Mode and Common Mode Differential amplifiers amplify the voltage difference which appears between the input and input This voltage is referred to as the Differential Mode or Normal Mode voltage The voltage component which is referenced to earth and is identical on both inputs is rejected by the amplifier This voltage is referred to as the Common Mode voltage and can be expressed as _ V Input V Input 2 Vom Differential Mode Range and Common Mode Range Differential Mode range is the maximum signal which can be applied between the and inputs without overloading the amplifier which otherwise would result in clipping or distorting the waveform measured by the oscilloscope The Common Mode Range is the maximum voltage with respect to earth ground which can be applied to either input Exceeding the common mode range can result in unpredictable measurements Because the Common Mode signal is normally rejected and not displayed on the oscilloscope you must be careful to avoid accidentally exceeding the common mode range Common Mode Rejection Ratio The ideal differential amplifier would amplify only the differential mode voltage component and reject all of the common mode voltage component Real differ
20. allowing the DA1855A to function as a true differential amplifier For most applications the Differential Offset Vpic mode has advantages over the Comparison Vcomp mode When using the Comparison mode the Precision Voltage Generator s output is subtracted from the INPUT Except for the PVG s offset operation is the same as a standard single ended oscilloscope only one DA1855A input is available In the Differential Offset mode the DA1855A functions as a differential amplifier both INPUT and INPUT function This allows the operator to choose a measurement reference point other than ground Even in ground referenced measurements signal degradation can be reduced by using the INPUT probe to select a ground reference point with the least noise This method is especially useful in eliminating hum and noise from ground loops There is one instance in which the Differential Offset Vpirr mode might result in more noise Magnetic pick up is proportional to the area between the probes If twisting the probe leads together is not sufficient to reduce magnetic pick up the Comparison Offset Vcomp mode may be preferable The Differential Offset VDIFF mode is usually the mode of choice if the wider range or higher accuracy of the Comparison VCOMP mode is not needed Avoiding Common Problems There are a few situations the operator of either the DA1855Ashould is aware of to avoid some potential measurement traps Exceeding th
21. from the Channel setup dialog for the channel to which it is connected The DA1855A front panel controls will operate manually when the Differential Amplifier is connected to an oscilloscope not provided with a ProBus interface NOTE Removing the ProBus interface cable with the differential amplifier still powered up requires the DA1855A to be turned OFF and ON to access the front panel controls Dynamic Range The basic amplifier dynamic range in X1 Gain and 1 Attenuation is 0 500 V Changing the gain and or attenuation will affect both the Differential Mode and Common Mode ranges The Differential Mode range is scaled by both gain and attenuation while the Common Mode range is scaled by attenuation only Gain Atten Geier Common Mode Mode 1 1 0 5V 15 5 V 1 10 5 0V 155 V 10 1 50 mV 15 5 V 10 10 0 5V 155 V Attenuation Common Mode and Differential Mode ranges are scaled with external probe attenuation A 10 probe will increase all these values by a factor of 10 11 DA1855A Differential Amplifier Front Panel Input Connectors Signals applied to the INPUT and the INPUT are connected either directly to the DA1855A amplifier s inputs or to the input attenuators Maximum input voltage is 200 Vp A signal connected to the INPUT will remain its polarity at the output connector A signal connected to the INPUT will be inverted in polarity Attenuators The input attenuators are pa
22. oscilloscope without an internal 50 termination Position the oscilloscope display to center screen Unless otherwise noted the oscilloscope position and offset must remain at zero for the duration of the verification procedure This procedure is written assuming local control of the DA1855A Differential Amplifier When using a Teledyne LeCroy oscilloscope do not use the ProBus cable Prior to performing the verification set the DA1855A as follows GAIN X1 ATTENUATOR 1 INPUT RESISTANCE 1M INPUT OFF INPUT OFF Vcomp OFF Vor OFF BANDWIDTH LIMIT FULL PVG ZERO OFFSET ZERO 58 Operator s Manual Functional Check The functional check will verify the basic operation of the Differential Amplifier functions It is recommended that the Functional Check be performed prior to the Performance Verification Procedure to assure that all other non warranted functions perform as specified To perform the functional check Select channel 1 of the oscilloscope and set the input coupling to DC 50 Q vertical scale to 100 mV div timebase to 10 usec div and adjust the trace to screen center Connect the output of the function generator with a BNC cable to channel 1 of the oscilloscope and set the output to square wave and the amplitude to 300 mV 3 div on screen Remove the function generator output cable from the oscilloscope ProBus operation a Connect the ProBus and the BNC cables to the output of the DA1855A and to cha
23. s Manual Rejecting the AC line voltage was no real challenge but rejecting the drain to source signal is a real measure of system ability The drain to source voltage rises over 245 Volt when the FET turns OFF The maximum rate of rise of this signal is about 15 V nsec followed by a ring at the bottom of the waveform It will be necessary to adequately reject this signal if upper gate signal is the be measured accurately Upper and Lower Gate Drive To examine the gate drive signal on the upper FET s Q1 the INPUT probe will be connected to the source of Q1 and the INPUT probe to the gate of Q1 The XC100 probes are set for an attenuation of 100 and the DA1855A for an attenuation of 1 and a gain of X1 The EFFECTIVE GAIN indicator should read an overall gain of 100 To make room for other traces the OFFSET control on the oscilloscope was set to 5 0 Volt moving the trace up one division The same procedure is repeated for Q2 gate drive where the OFFSET is set to 15 V to move the trace down by 3 divisions By setting mVOLT DIV to a more sensitive setting small details of these signals can be examined Avoiding Measurement Errors The math capabilities in modern digital oscilloscopes can save time and effort Both scalar measurements and waveform math provide direct answers for measurements that used to require considerable computation and analysis Common causes of erroneous results are e Errors in conditioning the input signal
24. voltage Change the oscilloscope s sensitivity from 5 mV div to 1 mV div Select Auto Zero in the List Select menu and push the button next to Auto Zero window to cause the DA1855A to adjust its DC balance Change the OFFSET control to again place the negative peak of the waveform at the oscilloscope s center screen Note that the Precision Voltage Generator s display represents the negative peak voltage of the waveform with greater resolution Return the oscilloscope s sensitivity to 50 mV div and select OFF or in the PVG Menu The Precision Voltage Generator will retain its setting and the display on the oscilloscope will be centered about 27 DA1855A Differential Amplifier the centerline Following are a few observations on using the DA1855A comparison voltage mode Vcome e The negative input and its AC OFF and DC coupling are disabled Instead of being a differential amplifier the DA1855A becomes a differential comparator It compares the voltage present at the INPUT with the output of the Precision Voltage Generator and when they are equal the output of the DA1855A is zero volts e The value displayed by the Precision Voltage Generator indicates a waveform s voltage with respect to ground as it passes through the oscilloscope display s centerline By using the DA1855A in the comparison voltage mode and the oscilloscope in a high sensitivity setting highly accurate voltage measurements can be made Different
25. voltage recorded in step 3 m Subtract this ratio from 1 and multiply by 100 to get the error in percent Expected Output x 100 Error 1 Measured Output Voltage Record the calculated error to two decimal places 0 xx as 10 Attenuation Error in the Test Record Check that the calculated error is less than 1 Disconnect the DMM sine wave generator cables and terminations but leave the amplifier output cable without termination connected to the DA1855A AMPLIFIER OUTPUT 67 DA1855A Differential Amplifier 68 4 Check X1 Bandwidth and Calculate Rise Time a Connect the DA1855A AMPLIFIER OUTPUT to channel 1 of the oscilloscope b Set the channel 1 input coupling to 50 Q NOTE If the oscilloscope does not have an internal 50 input termination insert the standard inline 50 termination between the cable and the oscilloscope input Use the standard wide bandwidth 50 termination The precision termination is not accurate at frequencies higher than 100 kHz c Verify that the DA1855A GAIN is set to X1 and the ATTENUATOR to 10 d Connect a BNC cable to the output of the leveled sine wave generator NOTE Many leveled sine wave generators including the SG503 are calibrated only when a special BNC cable is used on its output Be sure to use a cable which is specified for the generator e Insert a standard 50 Q termination on the free end of the cable and connect the termination to the
26. 94 dB 250 000 1 94 dB 2316 1 50 dB 0 05 of reading 500uV accuracy 15 C to 45 C Operator s Manual Typical Characteristics Typical characteristics describe parameters which do not have guaranteed performance Tests for typical characteristics are not provided in the Performance Verification Procedure Input Resistance 1 Attenuator 10 Attenuator Input Capacitance AC Input Coupling Capacitance 10 Attenuator Accuracy Bandwidth x10 Gain Common Mode Rejection Ratio Input Noise Overdrive recovery Output Zero Input Leakage Current Differential Offset Accuracy X10 Gain 1 Attenuator X1 Gain 1 Attenuator X10 Gain 10 Attenuator X1 Gain 10 Attenuator Precision Voltage Generator 1 MQ or 100 MQ 1 MQ only when used with attenuating probe 1 MO 20 pF 0 1 UF 0 05 100 MHz Refer to Figure 22 Refer to Figure 23 With DXC100A probe 100 Q between tip and ground In X10 gain settles within 1 mV referred to input within 100 nsec from 4 V input 8000 overdrive lt 2 mV referred to input lt 10 pA 0 C to 45 C 0 1 50 pV 0 1 500 pV 0 15 500 uV 0 15 5 mV lt 75 pV C Temperature Coefficient power consumption DA1855A DA1855A PR2 28 W 39 VA 56 W 78 VA z Output Zero is the output voltage from zero with zero Volt applied between inputs This specification is valid within 30 minutes from last Autozero cycle and when the differen
27. C13 connector for making line voltage and safety ground connections The AC inlet ground is connected directly to the frame of the instrument For adequate protection again electric shock connect to a mating outlet with a safety ground contact WARNING Interrupting the protective conductor inside or outside the device or disconnecting the safety ground terminal creates a hazardous situation Intentional interruption is prohibited Power On Off The Power On Off switch on the back of the amplifier controls the operational state of the device Press the side of the switch closest to either On or Off DA1855A Differential Amplifier Specifications These specifications are valid for instruments when the following conditions have been met e The instrument is being operated from a power source which meets the line voltage and frequency specifications e The instrument has been operating for at least 20 minutes in an environment which is within the operating environmental specifications e The instrument has been calibrated within the last 12 months Calibration was performed in a controlled environment of 25 C 5 C Nominal Characteristics Nominal characteristics describe parameters and attributes which are guaranteed by design but do not have associated tolerances General Input Configuration Offset Capability Input Coupling Selections Input Coupling Selection Input Connectors Maximum Input Voltage
28. Connect the function generator output to the INPUT BNC connector and apply a sine wave of 50 kHz and 1 0 Vp p amplitude If necessary set the oscilloscope scale factor to 0 50 V div The signal on the oscilloscope should be 2 divisions peak to peak Adjust the oscilloscope s time per division and trigger to display at least two complete cycles of the waveform Set the DA1855A Atten Gain to Manual In the List Select menu select Atten and in the Value menu select 1 The waveform s magnitude on the oscilloscope s display will increase by a factor of 10 to 50 mV div the waveform will extend and extend off the top and bottom of the screen The X1 light will be lighted in the EFFECTIVE GAIN front panel display Reduce the function generator s output until the oscilloscope s display is again 2 divisions peak to peak Set the gain to X10 Observe the following changes The INPUT s DC light will momentarily go out and its OFF light will be lighted before returning to their previous states This momentary change is the result of the DA1855A automatically adjusting its DC Balance The X10 light will be lighted in the EFFECTIVE GAIN display and the display on the oscilloscope will again extend off screen The overall sensitivity of the DA1855A and the oscilloscope is now 5mV div 26 Operator s Manual Comparison Voltage Operation Vcomp Set the DA1855A as follows PVG Mode OFF Coupling DC Coupling Grounded OFF DA1855A Atten G
29. Functional Test procedure 38 Operator s Manual Applications Some parts of a power supply operation such as saturation voltage upper gate drive loop response etc have been difficult to perform without the proper accessories to expand the measurement capabilities of oscilloscopes To obtain accurate voltage and current waveforms is a necessity before any waveform analysis can occur Voltage Measurements A significant limitation in power supply characterization is that many of the signals of interest are referenced to voltages other than ground Several techniques have been tried to overcome this measurement limitation The most frequently used and probably the worst one is floating the oscilloscope by disconnecting the ground wire in the power line cable This allows the chassis of the oscilloscope to float to the potential to which the probe ground lead is connected The most obvious danger is electrical shock When an oscilloscope is floated to hazardous voltages accidental contact with any metal component of the oscilloscope chassis can seriously injure or even kill the operator Another problem when floating a scope is the inability to externally trigger the oscilloscope or the waveform distortion that may occur when high slew rates appear on the ground lead Another technique used for measuring voltages not referenced to ground is quasi differential or channel A minus Channel B Even though this technique is safe t
30. G value of the DA1855A Differential Amplifier connected to the specified input channel The oscilloscope channel offset is always set to O Volt The maximum range and resolution is determined by the effective gain of the differential amplifier Refer to page 19 Table 2 Effective Offset Range with 11 Probe and Table 3 Effective Offset Range with 100 Probe for the list of available ranges Note The attenuation of any external probe is factored into the effective gain Changing or removing the probe from the differential amplifier may change the maximum range If an out of range value is entered the differential amplifier will set the PVG to the closest valid value and the VAB bit bit 2 in the STB register will be set The PRx OFFSET query returns the offset voltage of the differential probe connected to the specified channel lt channel gt OFfSeT lt voltage gt lt channel gt PR1 PR2 PR3 PR4 lt voltage gt See Table 2 Effective Offset Range with 11 Probe and Table 3 Effective Offset Range with 100 Probe for valid ranges lt channel gt OFfSeT lt channel gt OFST lt voltage gt The following command sets the PVG voltage of the differential amplifier connected to channel 1 to 6 38 Volt CMDS PR1 OFST 6 38 CALL IBWRT SCOPE CMDS 51 DA1855A Differential Amplifier Input Resistance PRx PINPUTR PRx PINR Command Query Description The PRx PINPUTR command sets the input
31. INPUT of the DA1855A Refer to Figure 16 Oscilloscope DA1855A Leveled Sine Wave Generator Front HOH 2 e ES mamap SC o ooo noooa Back Amplifier Output eb Geh Set Input Coupling Standard to DC 509 500 Attenuator Figure 16 X1 Bandwidth Check Setup f Set the leveled sine wave generator output frequency to 50 kHz and the amplitude to approximately 300mVp p g Set the oscilloscope Volt div to 50 mV div and the time div to 20 usec div Oscilloscope bandwidth to FULL Triggering to Channel 1 Adjust the trigger level for a stable display h Adjust the leveled sine wave generator output for an amplitude of exactly 6 divisions on the oscilloscope Operator s Manual i Set the sine wave generator output frequency to 50 MHz Be careful not to alter the output amplitude NOTE The displayed waveform will be compressed in time to form a solid rectangle It is not necessary to alter the time div setting as long as the peak amplitude can be measured j Slowly increase the output frequency of the leveled sine wave generator until the displayed amplitude decreases to exactly 4 2 divisions This is a 3 dB reduction in amplitude k Record in the Test Record the frequency where the 3 dB amplitude is obtained as Measured 3 dB Frequency at X1 Gain L Check that the frequency is gt 100 MHz m Divide 0 35 by the 3 dB frequency in Hz recorded in step 4 k The result i
32. L IBWRT SCOPE lt CMDS Operator s Manual Volt DIV PRx VOLT_DIV PRx VDIV Command Query Description When used with the PRx argument for channel number the VOLT DIV command sets the vertical sensitivity at the probe tip The effective gain of the differential amplifier including any attenuating passive probes is factored into the vertical sensitivity The command will also set the Atten Gain control mode to Auto if it was set to Manual mode The valid range of arguments is effected by the presence of an attenuating probe on the input If an out of range value is entered the oscilloscope will set the vertical sensitivity to the closest valid value and set the VAB bit bit 2 in the STB register The PRx VOLT_DIV query returns the vertical sensitivity at the probe input of the specified channel Command Syntax lt channel gt Volt_DIV lt sensitivity gt lt channel gt PRI1 PR2 PR3 PR4 lt sensitivity gt See page 11 Operation for valid arguments Query Syntax lt channel gt Volt_DIV Response Format lt channel gt VDIV lt sensitivity gt Example The following command sets the vertical sensitivity at the probe tip of the differential amplifier connected to channel 3 to 2 Volt div CMDS PR3 VDIV 2 CALL IBWRT SCOPE CMDS 55 DA1855A Differential Amplifier Performance Verification This procedure can be used to verify the warranted cha
33. Output Configuration Output Impedance Intended Output Load Output Connector Amplifier Gain Input Attenuation Bandwidth Limit Filters Low Pass Bandwidth Limit Filter Characteristics True Differential and Inputs Precision Voltage Generator can be selected as input source in Vcomp mode The Precision Voltage Generator can be used to provide true differential offset AC Off Precharge DC AC Off Precharge DC Vcome BNC Input incorporates Probe Attenuation Coding sensing connector Withstand up to 200 Vp continuous Automatic input disconnect with manual reset Single ended Ground referenced 50 O 50 O BNC X1 or X10 1 or 10 100 kHz 1 MHz 20 MHz or None full bandwidth 3 pole Bessel 18 dB octave Operator s Manual General continued Auto Zero Amplifier initiates an automatic balance cycle when either gain button is depressed to remove output offset drift Effective Gain Indicator Indicators show the effective system gain or attenuation factoring Probe Attenuation Attenuator and gain settings Probe must have coding connectors 1 10 100 and 1000 probes are recognized Dynamic Ranges Maximum Differential Mode Range X10 Gain 1 Attenuator 50 my X1 Gain 1 Attenuator 0 5 V X10 Gain 10 Attenuator 0 5 V X1 Gain 10 Attenuator 5 V Maximum Input Slew Rate 1 Attenuator 0 15 V usec 10 Attenuator 1 5 V usec Maximum Common Mode Range 1 Attenuator 15 5
34. This represents the actual voltage on the input of the amplifier Record the result as Amplifier Input Voltage in the Test Record Multiply the amplifier input voltage as recorded in step 2 v by 10 0 to obtain the expected output voltage Record the result to four digit resolution as Expected Amplifier Output Voltage in the Test Record After the DMM reading has stabilized record the measured voltage to 100 UV resolution as Measured Amplifier Output Voltage in the Test Record Calculate the error by dividing the expected output voltage recorded in step 2 w by the measured output voltage recorded in step 2 x Subtract this ratio from 1 and multiply by 100 to get the error in percent Expected Output lt j x 100 D r 1 Measured Output Voltage Record the calculated error to two decimal places 0 xx inthe Test Record as X10 Gain Error Check that the calculated error is less than 1 65 DA1855A Differential Amplifier 3 Check 10 Attenuator Accuracy a b 66 Remove the DA1855A output cable precision termination from the DMM Remove the sine wave generator output cable BNC Tee attenuator termination combination from the INPUT of the DA1855A Remove the BNC Tee and attenuator from the cable but leave the standard 50 O termination connected Connect the terminated output cable from the sine wave generator to the DMM using the BNC to Banana Plug adapter Refer to Figure 14 Standar
35. a TELEDYNE LECROY Everywhereyoulook Operator s Manual DA1855A Differential Amplifier DA1855A Differential Amplifier Operator s Manual August 2015 Zb TELEDYNE LECROY Everywhereyoulook a TELEDYNE LECROY Everywhereyoulook 2015 Teledyne LeCroy Inc All rights reserved Unauthorized duplication of Teledyne LeCroy documentation materials other than for internal sales and distribution purposes is strictly prohibited However clients are encouraged to distribute and duplicate Teledyne LeCroy documentation for their own internal educational purposes Teledyne LeCroy is a registered trademark of Teledyne LeCroy Inc Windows is a registered trademark of Microsoft Corporation Other product or brand names are trademarks or requested trademarks of their respective holders Information in this publication supersedes all earlier versions Specifications are subject to change without notice 926255 00 August 2015 Operator s Manual Table of Contents Safety INStrUCtlONS i c2 lt c c00c0cccceesscaceecencssseceeseesnscedensesectecnaeessaceeanevesnseesuecessecescarescuecseeedeacusncies 1 SVMDOIS coche shies ear ee EE dd ic Re 1 PRECAUTIONS EE E E sect en ee 1 Operating Environment c2 cccccc cide elias ene ieee 2 E el ue DEE 2 Cleaning BEE 2 Calibration WEE eege EES Specifications Nominal Characteristics ccccccccccessseceeeseceeeeeeeeeeeeneeeeesneeesceaeeeesceeeeeseeeesceeeesseneeeneneaes
36. achment to the circuit under test more convenient 10 and 100 attenuating probes also extend the common mode range of the differential amplifier For example the DA1855A amplifiers have a common mode range of 15 5 volts when their internal attenuators are set to 1 and 155 volts when set to 10 The addition of a probe with an attenuation factor of ten will extend the common mode range to 1550 volts or the rating of the probe whichever is less There is a trade off however The Common Mode Rejection Ratio CMRR capability of even highly matched differential probe pairs is seldom as good that of the amplifier In order to preserve as much of the amplifier s performance as possible at the probe tips it is important to use probes that are designed for differential performance Attempting to use normal 10 or 100 attenuating oscilloscope probes even high quality probes will result in very poor CMRR performance Nominally matching 1 probes however will provide excellent common mode rejection and are recommended For applications which do not require additional attenuation 1probes present relative high capacitive loading to the circuit under test limiting their usefulness to low frequency measurements When making differential measurements accurate probe compensation is much more important than in single ended measurements Most probes depend on the accuracy of the oscilloscope s 1 MQ input resistor to determine the accuracy of the probe
37. aeeeseteseaeeenates 35 Avoiding Common Problems A 35 Care and Mainte name cites ss 2occcsccciscbceadscscevecectssiedsene scce sede xx scde cqpccvesdexsexe scape ES 38 CIS AIAN DE 38 Calibration Intenal rnnt EEEEEEAAE Ennn EEEE EEn EEEE nanen n 38 Service Strategy eccececeesceeeseeeeseeesseeeeseeeeaeeeeaeeseaeeeaeeseaeeeeaeeseaeeseaeeseaeeesaeecsaeessasessaeeenaees 38 Troubleshooting spiris aai aiaeei 38 HEEN 38 DA1855A Differential Amplifier ee UL VT 39 Voltage Measurements ceececeeceseceeeeseneeseneeeeeeseecenenenaeeeeseeeeseseneeeesenseeeeseseeeeeieeenenees 39 Measuring Current ecceesccceseeeeneeeeneeseaeeseaeeseaeeseaeeseaeeseaeeeaeeseaeessaeesaeesaeeseaeeenaeeseaeeeaaee 39 Effects of Probes on Saturation Voltage Measuremerte 40 Saturation Voltage Measurement nt 43 Gate Drive VOltag EE 44 Upper and Lower Gate Drive cceccecsceeeseeeeneeeeeeeeeeeseaeeseeeeseaeeeaeeseaeeseateseaeeenaeessaeeeaaes 45 Avoiding Measurement Errors AAA 45 Remote Control Command isssiccssiceececevssncvcelesscecesciisctcectccnesettecucdessceescsdesnecectereseesstcoresctannneee 46 Command BC ete iesstt vive ett ie RR E A 46 Gain Control Mode oe 1tssee Eeer Ae NU 47 AUG MU AU OM eroen tei eee Bie LL Re 47 tre EE 48 Bandwidth LiMit ssia acetic EESEEE E 48 GOUPIING A E E He SU Rv ae 49 FT WEE 50 OTS C eegene eegend eege Eed 51 INPUt RESISTANCE cccscececs 20 jcecsececzcaastoceedsesoeecesecnsnecscce eesiseeusyeetetaey
38. ain Manual List Select Upper BWL FULL BWL List Select Gain X10 List Select Atten 1 List Select InputR1 MO Set the Function generator s output to 50 kHz and 100 mVp p sine wave and the output connected to the DA1855 s INPUT Set the oscilloscope to 5 mV div Under these conditions the display on the oscilloscope will extend off the top and bottom of the screen In the PVG Mode menu switch to Vcomp This internally applies the Precision Voltage Generator s output to the INPUT The OFF light on the DA1855A s front panel goes out and the Coupling menu on the user interface disappears the INPUT connector is disabled The positive and negative peaks of the waveform displayed on the oscilloscope are respectively 10 divisions above and below the display center line Rotate the OFFSET knob on the oscilloscope until the positive peak of the waveform appears in the oscilloscope s display Continue adjusting the OFFSET knob until the peak of the waveform is at the centerline of the oscilloscope s display The number in the Precision Voltage Generator display is the waveform s positive peak voltage Rotate the OFFSET knob clockwise until the negative peak of the signal is now at or near the oscilloscope s display centerline By adjusting the OFFSET knob the negative peak can be positioned to the oscilloscope s display centerline Now the number in the Precision Voltage Generator s display is the waveform s negative peak
39. are designed to maintain their accuracy for that portion of a signal that is displayed on screen When the signal is large enough to drive the display off screen the oscilloscope s amplifier must limit the signal in a non linear mode Oscilloscopes are designed so that no matter how the sensitivity position and offset controls are set the operator cannot view this distorted portion of the signal When used with a Teledyne LeCroy oscilloscope the setup is automatic to prevent you from entering a mode which could result in displaying a distorted signal resulting from overload When used with instruments lacking ProBus interface the instrument s gain and position controls should be properly set to avoid displaying the non linear portion of the DA1855A s output signal when it is in overdrive This can be accomplished by observing the following rules e Turn the oscilloscope input coupling to OFF or GND set the oscilloscope position control to center screen and do not change it If the oscilloscope has an OFFSET control it too should be set to zero Return the oscilloscope s input coupling to DC Subsequently adjust the trace position on the oscilloscope screen using the DA1855A PVG and Vor mode or Vcomp input This assures that the oscilloscope is set to the center of the DA1855A s dynamic range e Set the oscilloscope deflection factor to no greater than 100mV div The most useful range for the oscilloscope deflection fact
40. be controlled directly through the front panel controls Amplifier gain may be set to 1 or 10 A built in input attenuator may be separately set to attenuate signals by a factor of 10 allowing gains of 10 1 or 0 1 and common mode dynamic range of 15 5 V 1 or 155 V 10 Optional probes increase the maximum input signal and common mode ranges in proportion to their attenuation ratio but not exceeding their maximum input voltage rating Effective gain of the DA1855A including probe attenuation amplifier gain and attenuator settings is automatically displayed The DA1855A has a bandwidth of 100 MHz but any one of the three 3 pole bandwidth limit filters may be selected to reduce bandwidth to 20 MHz 1 MHz or 100 kHz to limit noise above the frequency of interest The DA1855A output is limited at 500 mV so that the oscilloscope is not overdriven by large inputs This allows an oscilloscope to directly measure the settling of D A converters with 14 bit 60ppm precision The DA1855A features a built in Precision Voltage Generator PVG that can be set to any voltage between 15 5 Volt 10 Volt in Differential Offset mode with 5 1 2 digit resolution Each digit of the voltage generator output can be individually incremented or decremented Positive or negative polarity can be selected The PVG s output can be selected as an input to the inverting input of the amplifier for operation as a differential comparator or applied inte
41. check that both of the DA1855A inputs are set to DC Record the Common Mode Feedthrough amplitude to two digit resolution in the Test Record as Common Mode Feedthrough at 10 MHz Calculate the Common Mode Gain by dividing the Common Mode Feedthrough in mV by 2 000 mV Record the result to two significant places as Common Mode Gain at 10 MHz in the Test Record Keep all of the leading zero s or use scientific notation Calculate the Common Mode Rejection Ratio CMRR at 10 MHz by dividing the Differential Mode Gain at 10 MHz as recorded in step 5 f by the Common Mode Gain recorded in step 5 y Record the result to two significant places as Common Mode Rejection Ratio at 10 MHz in the Test Record Keep all of the trailing zero s Check that the CMRR at 10 MHz is greater than 316 1 50 dB Disassemble setup by removing all cable adapters etc from the instruments 6 Check Low Frequency CMRR NOTE The attenuation of the DA1855A at 70 Hz and 100 ki is so insignificant that the Differential Mode Gain can be assumed to be unity 1 0 However the high value of the CMRR specification requires the zoom and averaging function to boost the level of the common mode feedthrough to an amplitude where it can be measured a Connect a BNC cable from the output of the high amplitude sine wave generator to the channel 1 input of the oscilloscope Do not terminate the cable into 50 Q and verify that channel 1 c
42. column and the replacement value in the body of the invoice marked For insurance purposes only e Bevery specific as to the reason for shipment Duties may have to be paid on the value of the service 85 DA1855A Differential Amplifier Teledyne LeCroy Service Centers Our regional service centers are World Wide Corporate Office Teledyne LeCroy 700 Chestnut Ridge Road Chestnut Ridge NY 10977 USA teledynelecroy com Sales and Service Ph 800 553 2769 845 425 2000 FAX 845 578 5985 contact corp teledynelecroy com Support Ph 800 553 2769 support teledynelecroy com US Protocol Solutions Group Teledyne LeCroy 3385 Scott Boulevard Santa Clara CA 95054 USA teledynelecroy com Sales and Service Ph 800 909 7211 408 727 6600 FAX 408 727 0800 protocolsales teledynelecroy com Support Ph 800 909 7112 408 653 1260 psgsupport teledynelecroy com European Headquarters Teledyne LeCroy SA 4 Rue Moise Marcinhes Case postale 3411217 Meyrin 1 Geneva Switzerland teledynelecroy com Europe Ph 41 22 719 2111 FAX 41 22 719 2230 contact sa teledynelecroy com 86 China LeCroy Corporation Beijing Rm 2001 Unit A Horizon Plaza No 6 Zhichun Road Haidian Dist Beijing 100088 China www lecroy com cn Sales Ph 86 10 8280031 8 0319 0320 FAX 86 10 82800316 Marketing China teledynelecroy com Service Rm 2002 Ph 86 10 82800245 Service China teledynelecroy com Korea Teledyne LeCro
43. condensation should be expected e Protection Class grounded equipment in which protection against electric shock is achieved by Basic Insulation and a connection to the protective ground conductor in the building wiring 83 DA1855A Differential Amplifier Environmental Compliance END OF LIFE HANDLING The product is marked with this symbol to indicate that it complies with the applicable European Union requirements to Directives 2002 96 EC and 2006 66 EC on Waste Electrical and Electronic Equipment WEEE and Batteries The product is subject to disposal and recycling regulations that vary by country and region Many countries prohibit the disposal of waste electronic equipment in standard waste receptacles For more information about proper disposal and recycling of your Teledyne LeCroy product please visit teledynelecroy com recycle RESTRICTION OF HAZARDOUS SUBSTANCES ROHS This product and its accessories conform to the 2011 65 EU RoHS2 Directive as it is classified as Industrial Monitoring and Control Equipment per Article 3 Paragraph 24 and is exempt from RoHS compliance until 22 July 2017 per Article 4 Paragraph 3 ISO Certification Manufactured under an ISO 9000 Registered Quality Management System 84 Operator s Manual Returning a Product Contact your local Teledyne LeCroy sales representative to find out where to return the product All returned products should be identified by model number and
44. cy components much higher than the repetition rate may suggests As such it is very difficult to predict actual performance in the application for CMRR versus frequency graphs The practical application of these graphs is to compare the relative common mode rejection performance between different amplifiers DA1855A Typical CMRR CMRR dB 10 100 1k 10k 100 k 1M 10M 100 M Frequency Hz Figure 22 Typical CMRR X1 X10 1000 100 Noise si z3 lt G 10 i j 10K 100K z Ei Ei Frequency Hz Figure 23 Noise Density Referred to the input 81 DA1855A Differential Amplifier Certifications EMC Compliance EC DECLARATION OF CONFORMITY EMC The amplifier meets intent of EC Directive 2004 108 EC for Electromagnetic Compatibility Compliance was demonstrated to the following specifications as listed in the Official Journal of the European Communities EN 61326 1 2013 EN 61326 2 1 2013 EMC requirements for electrical equipment for measurement control and laboratory use Electromagnetic Emissions EN 55011 2010 Radiated and Conducted Emissions Group 1 Class A Electromagnetic Immunity EN 61000 4 2 2009 Electrostatic Discharge 4 kV contact 8 kV air 4 kV vertical horizontal coupling planes EN 61000 4 3 A2 2010 RF Radiated Electromagnetic Field 3 V m 80 1000 MHz 3 V m 1400 MHz 2 GHz 1 V m 2 GHz 2
45. d 500 Sine Wave Terminator Generator Z IT EH o 5200000 8 papona C Te 128 hne S Output BNC to Dual Banana Plug Adaptor Figure 14 10 Attenuator Accuracy Set the sine wave generator to read 2 00 Vrms 50 mV on the DMM Record the reading as Sine Wave Generator Output Voltage to four digit resolution in the Test Record Divide the reading recorded in step 3 f by 10 00 and record the result as Expected Output Voltage to four digit resolution in the space provided in the Test Record Set the DA1855A GAIN to X1 and the ATTENUATOR to 10 Disconnect the sine wave generator output cable and standard 50 Q termination from the DMM and reconnect to the INPUT Remove the BNC to banana plug adapter from the DMM Connect the DA1855A AMPLIFIER OUTPUT cable precision termination to the DMM Refer to Figure 15 Operator s Manual DA1855A Sine Wave Generator Front Rear oo0000 a ES oooood o ocot poooo Ampiificr Outzut Precision ere W 500 Terminator Attenuator DMM ee ze P oOooooo H OO 08 Figure 15 10 Attenuator Accuracy Setup Press the X1 GAIN button to autozero the amplifier After the DMM reading has stabilized record the reading as Measured Amplifier Output Voltage to 100 UV resolution in the Test Record Calculate the error by dividing the expected output voltage recorded in step 3 g by the measured amplifier output
46. d result Using scale factors greater than 100 mV Div DOES NOT APPLY WHEN USING A TELEDYNE LECROY OSCILLOSCOPE WITH PROBUS INTERFACE know the input to the DA1855A is a sine wave but I am seeing a square wave on the oscilloscope This comment is the result of setting the oscilloscope Volt Div to something greater than 100 mV div If the oscilloscope sensitivity is set to 200mV div the DA1855A will limit at 2 divisions above and below center screen zero volt point if the oscilloscope s position control is properly set Thus a sine wave large enough to overdrive the DA1855A will appear as a square wave on the oscilloscope The DA1855A is designed to cleanly limit the output signal tot 500 mV The DA1855A goes into limit when its output reaches 500 mV and is designed to recover very quickly once its input signal level decreases sufficiently to allow the amplifier to return to its linear range The DA1855A will recover from overdrive to its full accuracy much more quickly than most oscilloscopes Keeping the 36 Operator s Manual oscilloscope s position at center screen and using oscilloscope sensitivities between 100 mV div and 2 mV div or the oscilloscope s most sensitive setting will insure good signal integrity When the displayed signal contains mostly low frequency components the operator can use the oscilloscopes 100 mV div setting to allow large signals to be completely shown on screen Failure to Terminate the
47. d waveform and to reduce noise NOTE This measurement needs to be made very carefully The signal is only several hundred uV in amplitude and measuring the peak to peak amplitude of this signal using oscilloscope measurement functions may cause erroneous reading Measure only the amplitude of the common mode feedthrough not the total value of the signal plus noise Record the displayed amplitude as Common Mode Feedthrough at 100 kHz to two digits resolution in the Test Record Calculate the Common Mode Gain by dividing the Common Mode Feedthrough in uV by 20 000 000 uV Record the result as Common Mode Gain at 100 kHz to two significant places in the Test Record Keep all of the leading zeros or use scientific notation Calculate the Common Mode Rejection Ratio CMRR at 100 kHz by dividing the Differential Mode gain at 70 Hz 1 0 by the Common Mode Gain recorded in step 6 bb Record the result as Common Mode Rejection Ratio at 100 kHz to two significant places in the Test Record Keep all of the trailing zeros 75 DA1855A Differential Amplifier bb Check that the CMRR at 100 kHz is greater than 50 000 1 94 dB cc Remove all cables terminations and adapters from the instruments 7 Check the Precision Voltage Generator Accuracy a k Connect a BNC cable from the DA1855A OFFSET VOLTAGE output connector on the rear panel of the DA1855A to the DMM input Do not use a 50 Q termination Pus
48. e Common Mode Range The DA1855A Differential Amplifiers have the largest common mode range available for this type of amplifier and are very good at measuring small differences between two large signals However care still must be taken not to allow a large common mode signal to exceed the available common mode range Unlike the differential mode signal which is viewed on the oscilloscope the common mode signal is normally rejected Thus you may not notice exceeding the common mode signal range The maximum common mode range is 15 5 Volt when a signal is applied directly 1 ATTENUATOR and no probes to theDA1855A s and INPUTs Attenuating the input signal extends the common mode range by the same factor as the attenuation Pressing the 10 ATTENUATOR button increases the common mode range to 155 Volt and using a probe with a 10 attenuation factor will too The effect of the internal 10 ATTENUATOR 35 DA1855A Differential Amplifier and the attenuation factor of probes is multiplied just as the signal is attenuated As an example using the amplifier s 10 ATTENUATOR with a probe having a 100 attenuation factor total attenuation of 1000 results in a common mode range of15 500 Volt In this case the probe s maximum voltage rating probably limits the maximum common mode input voltage The gain setting of the amplifier has no effect on common mode range it is the same in X10 GAIN as it is in X1 When making measur
49. e DA1855A to adjust its DC balance Change the OFFSET control to again place the negative peak of the waveform at the oscilloscope s center screen Note that the Precision Voltage Generator s display represents the negative peak voltage of the waveform with greater resolution Return the oscilloscope s sensitivity to 5 0mV div and select OFF in the PVG Menu The Precision Voltage Generator will retain its setting and the display on the oscilloscope will be centered about the centerline 29 DA1855A Differential Amplifier Following are a few observations on using the differential offset mode Vpr of the DA1855A e Both the positive and negative inputs AC OFF and DC are enabled and the DA1855A remains a true differential amplifier e The value displayed by the Precision Voltage Generator indicates a waveform s differential voltage with respect to the INPUT as it passes through the oscilloscope display s center line e By using the DA1855A in the differential offset mode and the oscilloscope in a high sensitivity setting high resolution voltage measurements can be made e The Precision Voltage Generator can be used as a position control which allows the DA1855A to operate in its most linear region Setting up the Oscilloscope without ProBus Interface Connect a 50 O coaxial cable between the AMPLIFIER OUTPUT BNC on the DA1855A rear panel and the oscilloscope s input connector If the oscilloscope has 1 MQ and 50 O in
50. ecision Voltage Generator and when they are equal the output of the DA1855A is zero volts e The value displayed by the Precision Voltage Generator indicates a waveform s voltage with respect to ground as it passes through the oscilloscope display s centerline It is very important that the oscilloscope s trace be positioned to center screen if an accurate measurement is to be made using this method 32 Operator s Manual e By using the DA1855A in the comparison voltage mode and the oscilloscope in a high sensitivity setting highly accurate voltage measurements can be made e The Precision Voltage Generator can be used as a position control which allows the DA1855A to operate in its linear region Differential Offset Operation VoiFF Leave the DA1855A set up as in the previous exercise or set it up as follows INPUT DC INPUT Vcomp BW LIMIT FULL GAIN X10 ATTENUATOR 1 INPUT RESISTANCE 1MQ PVG 0 0500 COMPARISON or COMPARISON DIFFERENTIAL EFFECTIVE GAIN X10 Set the Function generator s output to 50 kHz and 100 mVp p sine wave and the output connected to the DA1855A s INPUT Set the oscilloscope to 50 mV div equivalent to 5 mV div with DA1855A set at X10 GAIN and time div adjusted for 2 to 3 cycles Externally trigger the oscilloscope by connecting a cable from the function generator s output same signal as is applied to the DA1855A s INPUT or from the Trigger Signal out on the Function gene
51. eck to make sure the power switch located on the rear panel is in the OFF position Connect the power cable to an appropriate power source The DA1855A will operate on a 50 or 60 Hz AC power source with a nominal voltage range from 100 V to 240 V Comparator Mode The DA1855 becomes a differential comparator when the internal Precision Voltage generator PVG output is selected as the amplifier s inverting input The Input is disconnected form the amplifier and does not serve any purpose in the V comp mode In this mode the DA1855A can be used to very accurately measure relatively small signals riding on large DC components PYG Ot 155 Y Figure 1 Block Diagram Vcomp Mode Differential Mode The DA1855A built in Precision Voltage Generator can be used to generate a true differential offset while still allowing both inputs to be used as differential inputs This mode facilitates making measurements such as changes to a transistor s base to emitter voltage caused by variations in temperature Used in this mode the voltage generator can be set to a value that will zero out the static value of the junction s ON voltage the DA1855A s differential measurement capability will reject any dynamic signal common to both sides of the junction and the oscilloscope is left to measure only the changes in the junction voltage 24 Operator s Manual Coupling amp Aitcnuation PJG Ck_10 Lou amp Alfenuat
52. ecord as required by applicable internal quality procedures The section in the test record corresponds to the parameters tested in the performance verification procedure The numbers preceding the individual data records correspond to the steps in the procedure that require the recording of data Results to be recorded in the column labeled Test Result are the actual specification limit check The test limits are included in all of these steps Other measurements and the results of intermediate calculations that support the limit check are to be recorded in the column labeled Intermediate Results Permission is granted to reproduce these pages for the purpose of recording test results Serial Number DA1855A Asset Tracking Number Date Technician Equipment Used CALIBRATION MODEL SERIAL NUMBER DUE DATE OSCILLOSCOPE PREAMPLIFIER DIGITAL MULTIMETER LEVELED SINE WAVE GENERATOR HIGH AMPLITUDE SINE N A WAVE GENERATOR 1 The high amplitude sine wave generator is used in this Performance Verification Procedure for making relative measurements The output of this generator is measured with a DMM or oscilloscope in this procedure Thus the generator is not required to be calibrated 77 DA1855A Differential Amplifier DA1855A Test Record Step Description X1 Gain Accuracy 1 f Sine Wave Generator Output Voltage 1 k Amplifier Output Voltage 1 m X1 Gain Error Test limit
53. ectensiueeceianentiecniutanaameene 52 Probe AtlemU atin seiis raserny EE a ea Eain 53 Precision Voltage Generator 54 s 7A D EE 55 Performance VerifiCation ccssesceesseeesesscceeseseneesenscoeseseenerenscceesesenesseseesesensneeesesenenensenee 56 Test Equipment Required cccccceseeeesseeceeeneeeeeeseneeeeeeeeeeeeseeeensseseeseseeseeseseeeeenenaeeeniees 56 Preliminary Procequre iuz cici c etic sactestecescpadadccceatecctestecieciascepesdscseeensescenebic bisedeeaeessicazasteesd 58 F nctional GHOGK E 59 Verification Gite CEET 60 Performance Verification Test Record AAA 77 RROICKONCG iistviatacaeicadsaatavastandacadesstsnedaesasuideasiatansasnsdedeivaduasscatavedsancanadnadoastauusduedadusavssasessaasnsasensan 80 Differential Mode and Common Mode ssssseesiesseeseeeeteittsttsttstrnttntinnttnstnnttnntnnnnnstnnenn 80 Differential Mode Range and Common Mode Range ssssseesseeseesreererireresersrnsrnsrreeenn 80 Common Mode Rejection Ratio ccccecceeecesseeeeeeeeeneeeeeeeeeeeeeeeeeaeeseeeseeeseeeeeneeeeeeeteas 80 Certificats e iieiaeie aaea aaa a pE E A E EN SAN E deena 82 Returing Proguet TE 85 Teledyne LeCroy Service Centers cccceecceeseeeeneeeeeeeteneeseaeeseaeeseaeeseaeeeeaeeteaeessaeeseeeeeaeess 86 Waray EE 87 Operator s Manual Safety Instructions This section contains instructions that must be observed to keep this oscilloscope accessory operating in a correct and safe condition Yo
54. ed Do not use in wet or explosive atmospheres e Use indoors only DA1855A Differential Amplifier e Keep product surfaces clean and dry e Do not block the cooling vents Leave a minimum six inch 15 cm gap around the sides and back between the instrument and the nearest object The feet provide adequate bottom clearance Keep the underside clear of papers and other objects e Do not remove the covers or inside parts Refer all maintenance to qualified service personnel e Do not operate with suspected failures Do not use the product if any part is damaged Obviously incorrect measurement behaviors such as failure to calibrate might indicate impairment due to hazardous live electrical quantities Cease operation immediately and sequester the instrument from inadvertent use Operating Environment Temperature 0 to 50 C Humidity Maximum relative humidity 80 for temperatures up to 31 C decreasing linearly to 50 relative humidity at 50 C Altitude Up to 2 000 m 6 562 ft Cooling The instrument relies on forced air cooling with internal fans and vents Take care to avoid restricting the airflow to any part of the amplifier Around the sides and rear leave a minimum of 15 cm 6 inches between the instrument and the nearest object At the bottom the amplifier feet up or down provide adequate clearance CAUTION Do not block vents Always keep the area beneath the amplifier clear of paper and A other items
55. ed Probes which do not support probe code sensing will be reported having an attenuation of 1 Query Syntax lt channel gt PATTeNuation Response Format lt channel gt PATTN lt attenuation gt lt channel gt PR1 PR2 PR3 PR4 lt attenuation gt 1 10 100 1000 Example The following query reads the attenuation of the probe connected to the differential amplifier which is connected to channel 1 CMDS PR1 PATTN CALL IBWRT SCOPE CMDS CALL IBRD SCOPES lt RSPS PRINT RSPS Response message with a 100 probe attached ATTN 100 53 DA1855A Differential Amplifier Precision Voltage Generator Description Command Syntax Query Syntax Response Format Example 54 PRx PVGMODE PRx PVGM Command Query The PRx PVGMODE command sets the operating mode of the Precision Voltage Generator PVG of the differential amplifier The valid arguments are Vcomp Vor and OFF The PRx PVGMODE query returns the operating mode of the Precision Voltage Generator PVG of the differential amplifier connected to the specified channel lt channel gt PVGMode lt mode gt lt channel gt PR1 PR2 PR3 PR SC lt c 4 lt mode gt Vecomp Moss Or OFF hannel gt PVGMode hannel gt PVGM lt mode gt The following command sets the PVG operating mode of the differential amplifier connected to channel 3 to Voir CM DS PR3 PVGM Vbrrr CAL
56. ements on circuits that are power line referenced be sure to use enough total attenuation to keep the peak voltage at the amplifier input below 15 5 Volt The power line voltage in North America and Japan can exceed 170 Vp and therefore at least a total attenuation of 100 should be used Line voltages in some other countries are larger but their peak voltages do not exceed the 1550 Volt common mode range that a 100 attenuation factor provides Using the Oscilloscope POSITION control DOES NOT APPLY WHEN USING A TELEDYNE LECROY OSCILLOSCOPE WITH PROBUS INTERFACE When operating the DA1855A with a scope it is very important to set the oscilloscope s position and or offset control to center screen for several reasons First the linear portion of the DA1855A s 500 mV output range is centered around zero volts As the DA1855A begins to exceed its limits the output signal will be distorted Moving the oscilloscope s position control way from center screen can allow these distortions to appear on the oscilloscope s screen where they may be mistaken for part of the displayed signal Second proper operation of the DA1855A s Precision Voltage Generator PVG depends on the operator knowing the location of zero volts on the display The readout in the PVG is designed to display the voltage of the signal as it crosses the centerline of the oscilloscope screen If the oscilloscope s position or offset control has been moved incorrect readings coul
57. ence RFI from the signal This filter does not attenuate the PVG signal The PVG output is not attenuated by the input attenuator or probes whereas the input signal is Therefore the effective range of Vcomp is increased by a factor of 10 when the 10 ATTENUATOR is selected or a 10 attenuating probe is used to attenuate the input signal The PVG numerical display reflects the attenuator setting and probe attenuation when the probe is readout encoded As an example if there are no probes attached the 10 ATTENUATOR is selected and the display is set to read 155 000 the PVG output will actually be 15 5 Volt The decimal in the display will be in the correct location to indicate the voltage at the PVG output when no probes are attached and 1 ATTENUATOR and X1 GAIN are selected The OFFSET VOLTAGE BNC PVG output also presents the same voltage used internally for differential offset when Vpr is selected Because the PVG is applied to the amplifier to create a true differential offset the relationship between Vor and the voltage at the OFFSET VOLTAGE BNC PVG output changes with the amplifier gain selection according to the following table The maximum Moar is multiplied by any probe attenuation factor The DA1855A front panel displays the correct offset referred to the instrument input Table 1 Vp rr Range for Different Gain and Attenuator Settings Gain Attenuation Max Vor x1 1 10V X1 10 100 V X10 1 1V X10 10 10V
58. ential amplifiers are not perfect and a small portion of the common mode voltage component appears at the output Common Mode Rejection Ratio CMRR is the measure of how much the amplifier rejects the common mode voltage component CMRR is equal to the differential mode gain or normal gain divided by the common mode gain Common mode gain is equal to the output voltage divided by the input voltage when both inputs are driven by only the common mode signal CMRR can be expressed as a ratio e g 10000 1 or implicitly in dB e g 80 dB Higher numbers indicate greater rejection better performance The first order term which determines the CMRR is the relative gain matching between the and input paths To obtain high CMRR values the input attenuators in a differential amplifier are precisely matched to each other The matching includes the DC attenuation as well as the capacitance which determines the AC attenuation As the frequency of the common mode component increases the effects of stray parasitic capacitance and inductance in determining the AC component becomes more pronounced The CMRR becomes smaller as the frequency increases Hence the CMRR is usually specified in a graph of CMRR versus common mode frequency 80 Operator s Manual The common mode frequency in these graphs is assumed to be sinusoidal In real life applications the common mode signal is seldom a pure sine wave Signals with pulse wave shapes contain frequen
59. er Care and Maintenance Cleaning Clean only the exterior of the amplifier using a soft cloth moistened with water or isopropyl alcohol Using abrasive agents strong detergents or other solvents may damage the exterior of the amplifier Calibration Interval The recommended calibration interval is one year Adjustment should only be performed by qualified personnel A Performance Verification procedure is included in this manual Service Strategy Defective amplifiers must be returned to a LeCroy service facility for diagnosis and exchange A defective amplifier under warranty will be replaced with a factory refurbished one An amplifier that is not under warranty can be exchanged for a factory refurbished unit A modest fee is charged for this service A defective amplifier must be returned in order to receive credit for the amplifier core Calibration adjustments require the use of specialized signal sources which are not commercially available Amplifiers which do not pass the performance verification must be returned to the factory for service Troubleshooting If the amplifier is not operating properly the problem may be the way in which it is used Before assuming the amplifier is defective perform the Functional Test as described in the Performance Verification procedure Returns See Returning a Product on page 85 for instructions on returning an amplifier for repair if you determine it is malfunctioning after performing the
60. from 50mV div to 10mV div Overall sensitivity including the DA1855A is now ImV div Temporarily change the oscilloscope s input coupling from DC to GND or OFF and re center the trace to center screen using the oscilloscope s position control Return its input coupling to DC Now press the X10 button on the DA1855A to invoke its auto zero function Note that pressing the gain button that is already selected causes the DA1855A to adjust its DC balance but does not change its gain Change the Precision Voltage Generator s reading to again place the negative peak of the waveform at the oscilloscope s center screen Note that the Precision Voltage Generator s display represents the negative peak voltage of the waveform with greater resolution Return the oscilloscope s sensitivity to 50 mV div and press the DA1855A s INPUT OFF or AC or DC button The Precision Voltage Generator will retain its setting and the display on the oscilloscope will be centered about the centerline Press the Vcomp button on the INPUT again and observe that the Precision Voltage Generator s output is again connected to the INPUT of the DA1855A Following are a few observations on using the DA1855A comparison voltage mode Vcomp e The negative input and its AC OFF and DC coupling are disabled Instead of being a differential amplifier the DA1855A becomes a differential comparator It compares the voltage present at the INPUT with the output of the Pr
61. h the PVG ZERO button located at the lower left side of the Precision Voltage Generator display Set the DMM to DC Volts on the most sensitive range After the display has stabilized record the reading as PVG Zero Output Voltage in the Test Record Check that the measured 0 0000 V output is within 0 5 mV Set the DMM range to read 15 5 V Press and hold MSB increment button button to right of button until the display reads 15 500V If necessary press the button once to invert the polarity After the DMM display has stabilized record the reading as PVG Output Voltage at 15 5 V in the Test Record with 100 uV resolution CHECK That the measured output is within15 4917 to 15 5082 V Press the button to change the output voltage to 15 5000 V After the DMM display has stabilized record the reading as PVG Output Voltage at 15 5 V in the Test Record with 100 uV resolution Check that the measured output is within 15 4917 to 15 5082 V Disconnect DMM and all cables from amplifier This completes the Performance Verification Procedure File the test results as required to support your internal calibration procedures 76 Operator s Manual Performance Verification Test Record This record can be used to record the results of measurements made during the performance verification of the DA1855A Differential Amplifier Photocopy this page and record the results on the copy File the completed r
62. he center line Notice that the PVG retains its setting but the output of the PVG is not applied to the amplifier Press the Vor button again and observe that the Precision Voltage Generator s output is reapplied internally to the DA1855A amplifier Following are a few observations on using the differential offset mode Vos of the DA1855A e Both the positive and negative inputs AC OFF and DC are enabled and the DA1855A remains a true differential amplifier e The value displayed by the Precision Voltage Generator indicates a waveform s differential voltage with respect to the INPUT as it passes through the oscilloscope display s center line It is very important that the oscilloscope s trace be positioned to center screen if an accurate measurement is to be made using this method e By using the DA1855A in the differential offset mode and the oscilloscope in a high sensitivity setting high resolution voltage measurements can be made The INPUT is the reference for these measurements e The Precision Voltage Generator can be used as a position control which allows the DA1855A to operate in its most linear region 34 Operator s Manual Determining the Proper Offset Mode The operation of the Comparison Vcomp and Differential Offset modes Mot are quite similar The Comparison mode is easier to understand and has a wider range 15 5 Volt vs 10 0 Volt The Differential Offset mode provides offset operation while
63. he oscilloscope is still grounded it is still limited to measurements where the differential mode signal of interest is approximately the same amplitude or larger than the common mode signal signal being rejected A major problem however is the limited CMRR Common Mode Rejection Ratio caused by gain mismatches between the two input channels The best solution for measuring voltages that are not referenced to ground is to use a differential amplifier The DA1855 is ideally suited for these measurements Measuring Current Current can be measured either by using a shunt resistor or by using a current probe Adding a shunt resistor requires cutting the current carrying conductor Shunt resistors will add a resistance to the circuit that can affect the operation It is difficult to obtain accurate resistors with low resistance and low inductance values necessary to measure large dynamic currents Current probes overcome these problems Some models have a jaw that can be opened to install around conductors without the need to cut them They come in two different types AC and DC The DC types can measure from DC to higher frequencies with relative flat frequency response AC current probes have both a low frequency and a high frequency response Many AC current probes have a low frequency cut off of 40 Hz or higher eliminating the ability to measure power at line frequencies 39 DA1855A Differential Amplifier Effects of Probes on Saturati
64. he signal on screen is again about 3 division c Remove all cables accessories and return all setting of the DA1855A as shown in the table in the Preliminary Procedure Verification Procedure 1 Check X1 Gain Accuracy 60 a b Set the DA1855A INPUT to DC Connect the Sine Wave Generator output via a 50 Q BNC coaxial cable and a standard 50 Q termination to a female BNC to banana plug adapter Set the DMM to measure AC Volts Connect the banana plug adapter to the DMM Set the sine wave generator to 70 Hz and the output amplitude to read 200 mVrms 5 mV on the DMM Record the DMM reading to 100 uV resolution in the Test Report as Sine Wave Generator Output Voltage Disconnect the sine wave generator output cable with the 50 Q termination from the BNC to banana plug adapter on the DMM Connect this cable with the standard 50 Q termination to the INPUT of the DA1855A Remove the banana plug adapter from the DMM and connect the DA1855A AMPLIFIER OUTPUT connector via another coaxial cable and the precision 50 Q termination to the DMM See Figure 9 Operator s Manual DAIBSSA Sina Wave Generator Front Bank 2 E5 gege o Hb Ooo E e D DP DCH H oo acon E anew wll Su kan sier DMM K me SEO P 9 200000 SEA 10 Figure 9 X1 Gail Accuracy j Press the X1 GAIN button to remove any residual DC offset from the input A DC component may interfere with the RMS computation in some DMMs
65. hted In the line under the Precision Voltage Generator display COMPARISON or DIFFERENTIAL OFFSET the COMPARISON light went out and the DIFFERENTIAL light was lighted This indicates that the Precision Voltage Generator will now be applied as a differential offset rather than as a comparison voltage as in the previous exercise Both the INPUT and the INPUT inputs are now enabled even though the INPUT OFF light is still ON The positive and negative peaks of the waveform displayed on the oscilloscope are respectively 10 divisions above and below the display center line Rotate the OFFSET knob above the VOLTS DIV knob on the oscilloscope until the positive peak of the waveform appears in the oscilloscope s display Continue adjusting the oscilloscope s OFFSET knob until the peak of the waveform is at the centerline of the oscilloscope s display The number in the Precision Voltage Generator display is the waveform s positive peak voltage Rotate the OFFSET knob clockwise until the negative peak of the signal is now at or near the oscilloscope s display centerline By adjusting the OFFSET knob the negative peak can be positioned to the oscilloscope s display centerline Now the number in the Precision Voltage Generator s display is the waveform s negative peak voltage Change the oscilloscope s sensitivity from 5 mV div to 1 mV div Select Auto Zero in the List Select menu and push the button next to Auto Zero window to cause th
66. ial Offset Operation VoiFF Set the DA1855A up as follows through the oscilloscope user interface PVG Mode Coupling DA1855A Atten Gain List Select Upper BWL List Select Gain List Select Atten List Select Input R Vcomp DC Manual FULL BWL X10 1 1MQ Leaving the OFFSET control set as in the previous example the DA1855A front panel indicators should be lit as follows INPUT INPUT BW LIMIT GAIN ATTENUATOR INPUT RESISTANCE PVG COMPARISON or DIFFERENTIAL EFFECTIVE GAIN 28 DC Vcomp FULL X10 1 1MQ 0 0500 COMPARISON X10 Operator s Manual Set the Function generator s output to 50 kHz and 100 mVp p sine wave and the output connected to the DA1855 s INPUT Set the oscilloscope to 5 mV div and time div adjusted to display 2 to 3 cycles Externally trigger the oscilloscope by connecting a cable from the function generator s output same signal as is applied to the DA1855A s INPUT or from the Trigger Signal out on the oscilloscope Under these conditions the negative peak of the display on the oscilloscope should be very near center screen Adjust the OFFSET knob on the oscilloscope until the negative peak is at center screen Select Vpr in the PVG Mode window This internally applies the output of the Precision Voltage Generator to a point within the DA1855A s amplifier that facilitates a true differential offset The Vcomp light went out and the OFF light was lig
67. igure 7 Saturation Voltage Measurement To measure the saturation voltage of a power device in a flyback type switching power supply connect the INPUT probe to the drain and the INPUT probe to the source of the switching device There is no need to float the oscilloscope The probe connected to the INPUT becomes the reference lead same as black lead on a DMM The DA1855A will reject the power line portion common mode part of the signal and allows us to see the actual signal of interest Set the VOLTS DIV to 50 mV div and adjust the OFFSET to read 00 000 on the DA1855A front panel indicator Press the Auto Zero button to auto balance the amplifier The start of the saturation voltage measures close to 0 0 Volt since the switching device is OFF and ramps up due to the increase in current through the primary of the transformer If this starting point does not come close to the 0 Volt line then it could indicate an incorrect low frequency adjustment of the probes 43 DA1855A Differential Amplifier Gate Drive Voltage The main reason to measure the gate drive voltage is to assure rapid turn on and turn off and to assure that the transistor is fully saturated On h e A 12V al VI en a 5V Circuit Ground Power Supply Circuit Figure 8 Switching Power Supply with Upper and Lower FET Drive Care must be taken when acquiring the switching s device gate drive signal In off line switching power su
68. ion Figure 2 Block Diagram Vor Mode Setting Up the Oscilloscope with ProBus Interface Connect the RJ 45 type connector of the ProBus interface cable to the REMOTE connector and one end of the BNC cable to the AMPLIFIER OUTPUT on the rear panel of the DA1855A and the other end of the BNC cable to the ProBus connector Connect the ProBus connector to any vertical channel and if necessary press the Front Panel channel button to turn on the channel Switch the power switch located on the DA1855A s rear panel to ON and observe the front panel indicators Initially each indicator light will be ON and the red OVERLOAD indicator will be ON as well All segments in the Precision Voltage Generator display will be ON The INPUT and INPUT Coupling Indicators will switch to OFF while the amplifier performs the Auto Zero function and back to the original setting After approximately 3 seconds from turn on the DA1855A will return to the settings in effect when the power was last turned off The oscilloscope s input impedance has been set to 50 Q automatically through the ProBus interface the trace has been centered and all DA1855A front panel controls are locked out 25 DA1855A Differential Amplifier Make these settings PVG Mode OFF Coupling DC Coupling Grounded OFF DA1855A Aitten Gain Auto List Select Upper BWL Full BWL List Select Gain X1 List Select Atten 10 List Select Input R MO Attenuator and Gain Operation
69. ion 6 6 0 5 or higher Probe Coding Input This jack is to be used with Teledyne LeCroy DXC series probes to detect the probe attenuation factor Other manufacturer s probes with standard probe coding capability will be properly decoded through the DA1855A s front panel INPUT BNC connector Instrument Settings The DA1855A output is intended to connect directly to the input of an oscilloscope or other instrument but it is important to observe some rules so that the DA1855A delivers its specified performance CAUTION A properly terminated differential amplifier can deliver an output voltage of 0 5 Volt The output is DC coupled and will follow any DC component applied to the input Some instruments such as spectrum analyzers could be damaged from overload or DC components Retained Settings All front panel settings including Precision Voltage Generator PVG settings are retained when the instrument is turned off The DA1855A return to the same state they were in when power was removed 20 Operator s Manual When used without ProBus interface the instrument can be set to factory default settings by pressing the Vcomp and Vor buttons simultaneously Gain X1 Attenuation 10 Input Coupling Off Input Coupling Off Bandwidth Limit Full PVG Voltage 00 000 V Vcomp Off Vor Off Input Resistance 1 MQ PVG Mode Roll through zero Table 4 Factory Default Settings Sensitivity Position and Offset Oscilloscopes
70. is could damage sensitive circuits To avoid the inrush current transient it is therefore recommended that the INPUT coupling first be changed to the OFF precharge when measuring a new circuit point This will safely recharge the AC coupling capacitor in less than 0 3 seconds DC and low frequencies are attenuated by the AC coupling capacitor and the input resistance With the ATTENUATOR set to 10 or set to 1 with the INPUT RESISTANCE set to 1 MQ the low frequency cut off 3dB point is approximately 1 6 Hz When the input attenuator is set to 1 the 13 DA1855A Differential Amplifier INPUT RESISTANCE may be set to 100 MQ and the 3 dB point is 0 016 Hz This extremely low frequency cut off is useful for observing low frequency noise riding on larger DC voltages In the DC mode the INPUT connector is connected to the amplifier either directly or through the input attenuator and the AC and DC attenuation are the same Input Coupling AC OFF DC VCOMP The INPUT has the same coupling modes as the INPUT plus one additional option VCOMP comparison voltage The DA1855A contains a precision DC voltage source which is controlled by the oscilloscope OFFSET control When the amplifier is used stand alone without ProBus interface to a Teledyne LeCroy oscilloscope the voltage is controlled by the push buttons above and below the front panel numerical display This voltage source is called the Precision Voltage Gene
71. k After the DMM has stabilized record the reading to 100 uV resolution as Amplifier Output Voltage in the Test Record Divide the measured amplifier output voltage from step 1 k by the sine wave generator output voltage amplifier input voltage in step 1 f Subtract the ratio from 1 0 and multiply the result by 100 to get the error in percent Expected Output sec x 100 ERUF U Measured Output Voltage m Record the result to two decimal places 0 xx as X1 Gain Error in the Test Record n Check that the calculated X1 Gain error is less than 1 0 61 DA1855A Differential Amplifier 2 Check X10 Gain Accuracy NOTE Because most DMMs do not provide the required accuracy on lower AC voltage ranges the check for X10 Gain Accuracy uses a ratio technique with an external 10 attenuator The actual attenuation of the attenuator is determined using higher amplitude signals a Disconnect the DA1855A amplifier output cable and the precision 50 Q termination from the DMM b Disconnect the sine wave generator output cable from the INPUT and remove the 50 Q termination from the coaxial cable c Connect one female end of a BNC Tee to the sine wave generator cable d Connect a 50 Q 10 attenuator to the male end of the BNC Tee followed by a standard 50 Q termination e Reconnect the banana plug adapter to the DMM and connect another coaxial cable from the banana plug adapter to the other female end
72. l supplied with the oscilloscope Please refer to this manual for additional information on the remote control buses and the conventions used in the command descriptions Many of the commands begin with the PRx prefix where x is the channel which the DA1855A amplifier is connected to These commands are similar to the channel commands which use the prefix Cx The difference being that the PRx form refers to the probe tip whereas the Cx form refers to the oscilloscope input connector For example PRx VDIV sets the Volts per division at the probe tip while Cx VDIV sets the Volts per division at the BNC input connector without factoring the gain or attenuation factor of DA1855A amplifier and attached probes The PRx form of these commands are only active when the DA1855A amplifier is connected to the selected channel An error will result when an DA1855A specific command is sent to the oscilloscope without a differential probe attached to the selected channel Command List PRx ATTENUATION Selects the input attenuation of the amplifier PRx AUTOZERO Initiates an auto zero cycle in the amplifier PRx BWL Selects the upper bandwidth limit PRx COUPLING Selects the input coupling of the and inputs PRx GAIN Selects the gain of the amplifier PRx OFFSET Selects the Precision Voltage Generator voltage PRx PINPUTR Selects the input resi
73. lculate the Common Mode Rejection ratio CMRR at70 Hz by dividing the Differential Mode Gain at 70 Hz 1 0 by the Common Mode Gain recorded in step 74 aa Operator s Manual 6 p Record the result as Common Mode Rejection Ratio at 70 Hz to two significant places in the Test Record Keep all of the trailing zeros Check that the CMRR at 70 Hz is greater than 50 000 1 94 dB Remove the sine wave generator output cable from theDA1855A s input Reconnect the cable to the channel input of the oscilloscope Set the oscilloscope to display channel 1 The coupling to DC and 1 MQ the vertical scale to 5 V div and the horizontal scale to 5 us div If necessary adjust the trigger level for a stable display Set sine wave generator to 100 kHz Adjust the output amplitude of the sine wave generator to20 Vp p 4 divisions Readjust the oscilloscope trigger level of necessary to maintain a stable display Remove the sine wave generator output cable and reconnect it to the female to female BNC adapter and cables attached to the DA1855A inputs Refer to Figure 21 Connect the DA1855A output to channel 1 of the oscilloscope Set the oscilloscope to display channel 1 input coupling to DC and 50Q and the vertical scale as necessary to measure the amplitude of the displayed signal The displayed signal is the Common Mode Feedthrough Use the oscilloscope ZOOM function and averaging if needed to increase the size of the displaye
74. mance is required To overcome the overdrive problem is to use a specially designed fast clipping circuit to limit the magnitude of the signal at the oscilloscope s input to a value within the linear range and to turn ON and OFF fast enough so not to compromise the measurement integrity Another solution is to use a differential pre amplifier specifically designed to recover from being overdriven and to cleanly clip the signal so the oscilloscope is not overdriven Of equal importance to the amplifier s overdrive recovery performance is the oscilloscope or differential amplifier s probe performance Probes play an important role in device ON voltage measurements They attenuate the voltage s magnitude as well as provide a convenient way of connecting to the device under test in addition to attenuating 40 Operator s Manual the input signal they also attenuate the rate of change of the oscilloscope or differential amplifier s input signal A 100 passive probe will attenuate a 400 Volt signal with a dv dt of 10 V nsec to a 4 Volt signal with a dv dt of 0 1 V nsec Less obvious is the effect of a probe s low frequency compensation adjustment on the measurement accuracy of device saturation voltage Most oscilloscope users are familiar with the requirement of adjusting passive probes for low frequency compensation Under normal usage the entire waveform is on screen when a passive voltage probe s low frequency compensation is adjusted
75. maximum range of the PVG is 10 000 Volt in X1 GAIN and 1 0000 Volt in X10 GAIN The effects of the 10 input ATTENUATOR and probe attenuation are the same as when using VCOMP i e any input attenuation multiplies the effective offset The DA1855A s PVG display is changed to indicate the voltage that if applied between the INPUT and INPUT would bring the amplifier output to zero When the DA1855A is used with attenuating probes which feature readout the PVG display is scaled to include the effect of probe attenuation Effective Gain Six indicators LEDs across the top of the DA1855A front panel show the total gain from the instrument input to output Logic within the amplifier includes the gain internal attenuation and probe attenuation factors when readout encoded probes are used to determine the effective gain When the X1 light is ON the overall amplifier voltage gain amplification is unity Similarly X10 indicates an overall amplification of ten times 10 Indicates the voltage amplification is 0 1 etc The DA1855A communicates the effective gain information to the Teledyne LeCroy oscilloscope when the ProBus interface is used This corrects the scale factor of the displayed waveforms cursors and measurements When Teledyne LeCroy DXC series or other readout encoded probes are used the effective gain includes the probe s attenuator factor BW Limit FULL The DA1855A amplifier s full bandwidth over 1OOMHz is passed to
76. mination from the oscilloscope Attach to the 50 Q termination a female to female BNC adapter a BNC Y and a 6 BNC cable to each end of the BNC Y Set both the DA1855A INPUT and INPUT to DC Connect the two free ends of the 6 BNC cables to the DA1855A INPUT and INPUT Reconnect the AMPLIFIER OUTPUT cable to channel 1 of the oscilloscope Refer to Figure 19 Oscilloscope DA1855A Fe Front Back DDDDDD ps DDDDDD a noc D nnan n Amplifier Output A 8 Set Input Coupling to DC 50 2 Ka 6 BNC Cables BNC Y cL i Sine Wave Generator Frequency Le Reference Female to H Opu Female BNC Adapter 8 Standard D 50 Q Terminator Figure 19 HF CMRR Check Setup 71 DA1855A Differential Amplifier 72 aa bb CC Verify that the oscilloscope is set to display channel 1 and the input coupling to DC and 50Q Increase the channel 1 vertical sensitivity to maximum Verify that the oscilloscope is triggered on the Frequency Reference Signal Output of the sine wave generator Measure the peak to peak amplitude The displayed signal is the Common Mode Feedthrough Use the oscilloscope ZOOM function and averaging if needed to increase the size of the displayed waveform and to reduce noise NOTE The amplitude of the Common Mode Feedthrough should be very small If the output waveform appears to be 1 Volt square wave
77. mpedance circuits or when AC coupling is needed with a very low frequency cut off When the input ATTENUATOR is set to 10 or an attenuating probe with read out capability is attached 1 MQ 1M input resistance is automatically selected 12 Operator s Manual Unbalanced source impedances can have an adverse effect on common mode rejection For example a differential source with impedances of 1000 and 2000 Q each loaded with 1 MQ will have a common mode rejection ratio CMRR of 1000 to 1 The common mode rejection ratio can be improved to 100 000 to 1 by using 100 MO input resistance Auto Zero Auto Zero is a feature invoked from the Channel setup dialog when the amplifier is connected via the ProBus interface If the Differential Amplifier is not connected through a ProBus interface push either the X1 or X10 button even if a different gain is not selected Auto Zero momentarily sets the input coupling to OFF and determines the offset necessary to set the output at O Volt During this process the front panel input signal to the amplifier is interrupted When the Auto Zero cycle is completed the input coupling returns to its previous state Auto Zero usually takes less than one second to complete This feature allows you to DC balance the DA1855A simply by pushing the GAIN button which is already illuminated When changing gains the Auto Zero feature is automatically invoked adjusting the amplifier s DC balance Input Coupling AC
78. n charges prepaid This warranty replaces all other warranties expressed or implied including but not limited to any implied warranty of merchantability fitness or adequacy for any particular purposes or use Teledyne LeCroy shall not be liable for any special incidental or consequential damages whether in contract or otherwise 87 DA1855A Differential Amplifier 88 926255 00 August 2015 K TELEDYNE LECROY Everywhereyoulook F 700 Chestnut Ridge Road Chestnut Ridge NY 10977 USA teledynelecroy com
79. nd Media Authority ACMA EN 55011 2010 Radiated and Conducted Emissions Group 1 Class A in accordance with EN61326 1 2013 and EN61326 2 1 2013 Australia New Zealand Contacts RS Components Pty Ltd RS Components Ltd Suite 326 The Parade West Unit 30 amp 31 Warehouse World Kent Town South Australia 5067 761 Great South Road Penrose Auckland New Zealand Safety Compliance EC DECLARATION OF CONFORMITY LOW VOLTAGE The amplifier meets intent of EC Directive 2006 95 EC for Product Safety Compliance was demonstrated to the following specifications as listed in the Official Journal of the European Communities EN 61010 1 2010 Safety requirements for electrical equipment for measurement control and laboratory use Part 1 General requirements EN 61010 2 030 2010 Safety requirements for electrical equipment for measurement control and laboratory use Part 2 030 Particular requirements for testing and measuring circuits The design of the amplifier has been verified to conform to the following limits put forth by these standards e Measurement Category Il equipment intended to be supplied from the building wiring with a nominal supply voltage up to 300V e Measurement Category 0 amplifier measurement terminals that are not intended to be directly connected to the MAINS supply e Pollution Degree 2 operating environment where normally only dry non conductive pollution occurs Temporary conductivity caused by
80. ne must be specified at time of order e Option P01 120 V North America Japan e Option P02 United Kingdom e Option P03 Universal Europe e Option P04 Australia New Zealand e Option P05 Switzerland Standard Accessories Each DA1855A Differential Amplifier is packaged for shipment with the following items e Power cable as specified by power cable option e ProBus interface cable with BNC signal cable PR2 models include 2 ProBus cables e Certificate of Calibration traceable to NIST United States National Institute of Standards and Technology e Operator s Manual which includes a Performance verification Procedure 10 Operator s Manual Optional Accessories e Service Manual containing adjustments repair and replacement part information P N DA1855A SM E e DXC100A 10 100 Passive Differential Probe e DXC200 1 Passive Differential Probe e DXC5100 100 2 5 K Passive Differential Probe Pair e DA101 External 10 Attenuator Operation General Information The DA1855A has been designed to be used with oscilloscopes equipped with a ProBus interface Connecting the Differential Amplifier to the oscilloscope through the ProBus interface will automatically control all the required settings from the oscilloscope and will lock out the DA1855A front panel controls All front panel controls are now accessible through the oscilloscope user interface The DA1855A user interface can be viewed
81. nnel 1 of the oscilloscope b Verify that channel 1 is selected and that the DA1855 is being recognized by showing DA1855A on the screen s menu Coupling a Connect the 300 mV output voltage of the square wave generator to the INPUT of the DA1855A b Verify that the trace is a single line centered on the screen c Press the DC button on the INPUT of the DA1855A and verify that the trace has moved either up or down depending on the polarity of the signal and that DC is highlighted on the screen s menu d Press the AC button on the INPUT and verify that the input signal is centered on screen and AC is highlighted on the screen s menu e Disconnect the function generator s output signal from the INPUT and connect it to the INPUT f Verify the performance of steps 2 b through 2 d for the input 59 DA1855A Differential Amplifier 3 Bandwidth Limiting a Press the 10 MHz BW Limit button on the front panel of the DA1855A and verify that the slope of the trace s leading and trailing edge has decreased b Press the resp 1 MHz and 100 kHz BW Limit buttons and verify that in each case that the slope of the leading and trailing edges decreases c Return to maximum bandwidth by pressing the FULL BW Limit button 4 X10 Gain and 10 Attenuator a Press the 10 attenuator button and verify that the signal on screen has reduced by about a factor of 10 b Press the X10 Gain button and verify that t
82. nt of the PVG polarity Decrements from a positive voltage will roll smoothly through zero This is known as roll through zero mode Toggle PVG modes To change from roll through zero to absolute mode of operation hold the PVG ZERO button and press the button Change back to the roll through zero mode by repeating the same operation 15 DA1855A Differential Amplifier Differential Offset Voir differential offset voltage is an instrument mode rather than a type of input coupling The Vo mode allows the PVG to inject a calibrated offset signal into the DA1855A while still using both inputs for full differential operation This mode can be used as a position control to move the trace on the oscilloscope screen in preference to using the oscilloscope s position or offset control The oscilloscope s position and offset controls should always be set to zero so that the DA1855A s dynamic range is properly centered This is done automatically when using a Teledyne LeCroy oscilloscope with ProBus interface When the oscilloscope is set to greater sensitivities lower Volts Div settings the Differential offset provides much greater range than the conventional position control For example at 50 mV div the Vor mode provides up to 200 divisions of range Operation of the DA1855A using the Vor function is the same as Vcomp except for the following e The INPUT remains active allowing full use of the DA1855A as a differential amplifier e The
83. of test instruments additional adapters or cables may be required 56 Description Wide Band Oscilloscope Minimum Requirements 500 MHz bandwidth 2 mV 200mv scale factors 1 ns 10 us sweep speed 2 vertical accuracy 50 Q termination Table 5 List of required Equipment Operator s Manual Test Equipment Examples Teledyne LeCroy LT374 series oscilloscope Digital Multimeter DC 0 01 accuracy AC 0 2 accuracy to measure 200 mV and 2 Vrms 1 kHz 6 digit resolution HP 34401A Fluke 8842A 09 Keithley 2001 Oscillator Function Generator Sine Wave output 20 Vp p at 70 Hz Stanford Research Model DS340 Hewlett Packard 33120A Leader LAG 120B Leveled Sine Wave Generator Terminator in line BNC Relative output level accurate to 0 5 dB flatness from 1 100 MHz and 50 kHz Output adjustable to 2 Vp p 50 Q 2 coaxial termination Tegam SG503 with TM series mainframe and 012 0482 00 output cable ITT Pomona 4119 50 AIM 27 9008 Terminator precision BNC 50 Q 0 05 Teledyne LeCroy TERM CFO1 Attenuator BNC 50 Q 2 10 20 dB ITT Pomona 4108 20dB AIM 279300 20 BNC coaxial cable 3 ea BNC coaxial cable 2 ea Male male BNC 50 Q 36 Male male BNC 500 4 6 ITT Pomona 5697 36 Pasternack Enterprises PE3067 5 BNC Y connector Male to dual female BNC AIM 27 9294 BNC Tee connector Male to dual female BNC AIM 27 8140
84. of the BNC Tee See Figure 10 f Set the sine wave generator output amplitude to read 2 00 Vrms 50 mV on the DMM DH g Record the reading to 1 mV resolution as the Sine Wave Generator Output Voltage in the Test Record eener O m am les onooooom o EES ok Sp Output Figure 10 X10 Gain Accuracy Setup 62 Operator s Manual Remove the DMM cable from the BNC Tee and from the banana plug adapter on the DMM Connect the 50 Q termination end of the termination attenuator BNC Tee combination on the sine wave generator cable to the Banana Plug adapter on the DMM See Figure 11 Sine Wave DMM Lexem DA Zb ch Ec Iesel eslesleslesl es b accan A j BNC lo Dual 10 Attenuator Hanana Pluy Figure 11 X10 Gain Accuracy Setup Record the DMM reading to 100 uV resolution as Attenuator Output Voltage in the Test Record NOTE This reading should be approximately 200 mV If it is not verify that the in line attenuator and termination are installed in the correct order The 50 Q termination should be closest to the DMM Divide the DMM reading in step 2 j into the output amplitude measured in step 2 g This is the exact attenuation of the attenuator termination combination Record the result as Exact Attenuation to four digit resolution in the Test Record Disconnect the termination attenuator BNC Tee combination from the Banana Plug adapter on the DMM
85. on Voltage Generator display is the value of the waveform s positive peak voltage Press the button in the Precision Voltage Generator Observe that the negative peak of the signal is now at or near the oscilloscope display s center line By incrementing and decrementing the digits the negative peak can be positioned to the oscilloscope display s center line Now the number in the Precision Voltage Generator s display is the value of the waveform s negative peak voltage Change the oscilloscope s sensitivity from 50 mV div to 10 mV div Overall sensitivity including the DA1855A is now 1 mV div Temporarily change the oscilloscope s input coupling from DC to GND or OFF and re center the trace to center screen using the oscilloscope s position control Return its input coupling to DC Now press the X10 button on the DA1855A to invoke its Auto balance function Note that pressing the gain button that is already selected causes the DA1855A to adjust its DC balance but does not change its gain Change the Precision Voltage Generator s reading to again place the negative peak of the waveform at the oscilloscope s centerline Note that the Precision Voltage Generator s display more accurately represents the negative peak voltage of the waveform Return the oscilloscope s sensitivity to 50 mV div and again press the DA1855A s Vpirr button The Voie light will go out and the display on the oscilloscope will be centered about t
86. on Voltage Measurements To measure switching s device saturation voltage while the device is operating in circuits requires the combination of several capabilities in the measurement system First because the measurements are not ground referenced thus differential voltage measurements are needed The amplifier must also be able to quickly recover from overdrive and the amplifier as well as the probes must have very low high frequency aberrations VOFF Vos Saturation Voltage Figure 3 Saturation Voltage The most obvious problem with this measurement is the signal s wide dynamic range The voltage across the device can be several hundred Volt when the device is off and then drop to less than a Volt as the device turns on Figure 3 To measure the saturation voltage of a device to 100 mV accuracy when the OFF voltage is 400 Volt requires 250 ppm measurement capability To accurately view the device s approximately 1 Volt ON voltage with an oscilloscope the vertical sensitivity must be set to 200 to 500 mV div Almost all of the signal will be off screen Also this voltage change occurs in a fraction of a microsecond This means that the oscilloscope must be able to accurately display sub 1 Volt signal less than a microsecond after being overdriven by several hundred divisions It is obvious that the oscilloscope input or an input preamplifier such as the DA1855A needs to recover and therefore that a probe with high frequency perfor
87. ors will be between 1mV div and 100mV div Using a scale factor of 200 mV Div will allow the nonlinear portion of the DA1855A s output to be viewed on screen 21 DA1855A Differential Amplifier More sensitive settings e g 100uV div available on some oscilloscopes can be used but their usefulness may be limited by noise particularly with the DA1855A FULL bandwidth limit selection and without averaging With the oscilloscope set to 100uV div and the DA1855A in the X10 GAIN mode the overall scale factor will be 10uV div In the X10 GAIN mode the DA1855A has lower noise than many oscilloscopes so it is preferable to use the DA1855A X10 GAIN mode and a lower oscilloscope scale factor For example to obtain the best noise performance at 1mV div set the DA1855A to X10 mode and the oscilloscope to 10mV div rather than the use X1 mode and 1mV div This also maximizes the bandwidth as some oscilloscopes give up some bandwidth at their most sensitive settings Some oscilloscopes give up bits of resolution to obtain 1mV or 2 mV div sensitivity The loss of resolution can be avoided by using this technique Any oscilloscope bandwidth limit setting may be used so long as the unlimited signal does not exceed full screen before invoking bandwidth limit Probes and Differential Amplifiers When using a differential amplifier it is very important to understand the role probes play in the overall measurement system performance Probes not only make att
88. oupling is set to DC and 1MQ Operator s Manual Connect a BNC cable from the Frequency Reference Signal Output of the leveled sine wave generator to the External Trigger Input of the oscilloscope If the sine wave generator does not have a Frequency Reference Signal Output insert a BNC Tee adapter into the Output connector and attach the External Trigger BNC cable to the BNC Tee Oscilloscope External Trigger Input Frequency Reference Output High Amplitude Sine Wave Generator Figure 20 LF CMRR Check Setup Set the oscilloscope to display channel 1 vertical scale to 5 V div and time base to 10 ms div Set the sine wave generator frequency to 70 Hz Set the high amplitude output of the sine wave generator to exactly 20 Vp p 4 divisions Adjust the oscilloscope trigger level as necessary for a stable display Take care not to alter the sine wave generator settings during the following steps Remove the sine wave generator output cable from the oscilloscope input Connect the open end of this cable to the female to female BNC adapter a BNC Y and a 6 BNC cable to each end of the BNC Y Connect the two free ends of the 6 BNC cables to the INPUT and INPUT of the DA1855A Refer to Figure 21 Verify that both the INPUT and INPUT of the DA1855A are set to DC Connect another BNC cable from the AMPLIFIER OUTPUT on the DA1855A under test to channel 1 of the oscilloscope
89. pplies the switching devices are elevated to line potential The DA1855A is ideally suited for this application with its high CMRR The following discussion demonstrates how the DA1855A Differential Amplifier and a XC100 Differential Probe are used to make measurements such as upper gate drive signal on a switching power supply A simplified schematic of such a flyback type power supply is shown in Figure 8 In this circuit both Q1 and Q2 are ON at the same time D1 and D2 limit the voltage caused by the primary s leakage reactance to the rail voltages By using the DA1855A and the XC100 probe the signal reference point can be changed to any point in the circuit To select the source of Q2 as the reference point connect the INPUT probe to that point To acquire the drain to source signal of Q2 place the INPUT probe on the drain of Q2 and select DC coupling on both inputs The amplifier will reject the power line portion common model of the signal and allows us to see the drain to source signal For this measurement the XC100 is set to 100 and the DA1855A is set for 10 attenuation and a gain of X1 The total attenuation from probe tip to the oscilloscope is 1000 Selecting the differential mode and setting the OFFSET to 245 Volt will move the trace down about 2 divisions This means that the drain voltage with respect to the source is 245 Volt when the top part crosses the oscilloscope s screen horizontal center line 44 Operator
90. put capability select 50 Q If the oscilloscope has only a 1 MQ input terminate the coaxial cable at the oscilloscope s input with a 50 Q feed through terminator It is important that the DA1855A be terminated by 50 Q Set the oscilloscope vertical scale factor to 50mV div Set the oscilloscope s input coupling to GND or OFF and position the trace to center screen Do not move the oscilloscope position setting after this initial set up Change the oscilloscope input coupling to DC Change the power switch located on the DA1855A s rear panel to 1 ON and observe the DA1855A s front panel indicators Initially each indicator light will be ON and the red OVERLOAD indicator will be ON as well All segments in the Precision Voltage Generator display will be ON After approximately 3 seconds the DA1855A will return to the settings in effect when the power was last turned off Set the DA1855A as follows INPUT DC INPUT OFF BW LIMIT FULL GAIN vi ATTENUATOR 10 INPUT RESISTANCE 1MQ PVG 00 000 COMPARISON or COMPARISON DIFFERENTIAL EFFECTIVE GAIN 10 30 Operator s Manual Attenuator and Gain Operation Connect the function generator output to the INPUT BNC connector and apply a sine wave of 50 kHz and 1 0 Vp p amplitude The signal on the oscilloscope should be 2 divisions peak to peak amplitude Adjust the oscilloscope s time per division and trigger to display at least two complete cycles of the waveform Press the
91. r GND lt coupling gt AC DC or GND ignored when PVG Mode is set to Vcomp Query Syntax lt channel gt CouPLing Response Format lt channel gt CPL lt coupling gt lt coupling gt Example The following command sets the input coupling to DC and the input coupling to ground for the differential amplifier connected to channel 2 CMDS PR2 CPL DC GND CALL IBWRT SCOPE CMDS 49 DA1855A Differential Amplifier Gain Description Command Syntax Query Syntax Response Format Example 50 PRx GAIN PRx GAI Command Query The PRx GAIN command sets the differential amplifier gain The command will also switch the Atten Gain control mode to Manual if it was in Auto The valid arguments are 1 and 10 The PRx GAIN query returns the gain of the differential amplifier connected to the selected channel lt channel gt GA PR4 lt gain gt 1 lt channel gt GAI n lt channel gt GA In lt gain gt In lt gain gt lt channel gt PR1 PR2 PR3 10 The following commend sets the gain of the differential amplifier connected to channel 1 to X10 CMDS PR1 GAI 10 CALL IBWRT SCOPE CMDS Operator s Manual Offset Description Command Syntax Query Syntax Response Format Example PRx OFFSET PRx OFST Command Query The PRx OFFSET command sets the Precision Voltage Generator PV
92. racteristics of the DA1855A Differential Amplifier The recommended calibration interval for this Differential Amplifiers is one year The complete performance verification procedure should be performed as the first step of annual calibration Test results can be recorded on a photocopy of the Test Record provided in Appendix A Performance verification can be completed without removing the instrument covers or exposing you to hazardous voltages Adjustment should only be attempted if a parameter measured in the Performance Verification Procedure is outside of the specification limits Adjustment should only be performed by qualified personnel Removing the covers from the instrument may alter critical compensation adjustments requiring the instrument to be recalibrated Re establishing these adjustments requires the use of special calibration fixtures Therefore never remove the covers The Adjustment Procedure is contained in the Service Manual Test Equipment Required The following table lists the test equipment and accessories or their equivalents which are required for performance verification of the DA1855A This procedure has been developed to minimize the number of parameters required to be calibrated in the test instrumentation Only the parameters listed in boldface in the Minimum Requirements column must be calibrated to the accuracy indicated Because the input and output connector types may vary on different brands and models
93. rator PVG The DA1855A s amplifier subtracts the voltage applied to its inverting input from the voltage applied to its non inverting input The DA1855A output is therefore zero whenever these two voltages are equal For this reason the voltage applied to the inverting input is called a comparison voltage VCOMP Stated another way the value of the horizontal center line in the oscilloscope graticule is the voltage read in the PVG display Each graticule line above or below the center line will add or subtract the Volts div value from the PVG setting VCOMP can be used to make precise measurements of large signals by comparing the accurately known VCOMP with the unknown signal It can also be used to measure the actual voltage at any point of a waveform Since the amplifier s gain and input attenuator are individually selectable the comparison range can be changed from 15 500 V to 155 000 V by changing the ATTENUATION from 1 to 10 while the overall gain can still be set either to 1 or 0 1 by selecting either X10 or X1 GAIN NOTE While in Vcomp mode the amplifier is configured for single ended measurements The INPUT connector is not usable when Vcomp is selected The input signal applied to the INPUT is referenced to ground offset by the value set by the Precision Voltage Generator Large calibrated offsets can be obtained while making differential measurements by using Moar Mode Precision Voltage Generator The PVG generates
94. rator to the External trigger input of the oscilloscope Under these conditions the negative peak of the display on the oscilloscope should be very near center screen Adjust the value in the Precision Voltage Generator until the negative peak is at center screen Press the VDIFF button This internally applies the output of the Precision Voltage Generator to a point within the DA1855A s amplifier that facilitates a true differential offset The VCOMP light went out and the OFF light was lighted In the line under the Precision Voltage Generator display COMPARISON or DIFFERENTIAL OFFSET the COMPARISON light went out and the DIFFERENTIAL light was lighted This indicates that the Precision Voltage Generator will now be applied as a differential offset rather than as a comparison voltage as in the previous exercise Both the INPUT and the INPUT inputs are now enabled 33 DA1855A Differential Amplifier The positive and negative peaks of the waveform displayed on the oscilloscope are 10 divisions above and below respectively the center line of the display Push the button above the digit that is two places right of the decimal 10mvV in the Precision Voltage Generator until the positive peak of the waveform appears in the oscilloscope s display Continue incrementing and decrementing the digits in the Precision Voltage Generator until the peak of the waveform is at the center line of the oscilloscope s display The number in the Precisi
95. resistance for both inputs of the differential amplifier The valid arguments are 1M or 100M when the differential amplifier input attenuation is set to 1 and an attenuating probe is not being used When an attenuating probe is attached to the differential amplifier or the internal attenuation is set to 10 only 1M may be selected The units of the arguments are Ohm The PRx P NPUTR query returns the input resistance setting for the differential amplifier connected to the specified channel Command Syntax lt channel gt P PR2 PR3 PR4 NputR lt input resistance gt lt channel gt PRI1 lt input resistance gt 1M or 100M when the internal attenuation is 1 without attenuating probe or 1M when the internal attenuation is 10 or an attenuating probe is used Query Syntax lt channel gt PINputR Response Format lt channel gt PINR lt input resistance gt Example The following command sets the input resistance of the differential amplifier connected to channell to 1 MQ CM 52 DS PR1 P INR 1M CALL IBWRT SCOPE CMDS Operator s Manual Probe Attenuation PRx PROBEATTENUATION PRxPATIN Query Description The PRx PROBEATTENUATION query returns the attenuation value of the probe connected to the input of the DA1855A Only probes which support probe code sensing will be correctly reported Attenuation values of 1 10 100 or 1000 are sensed and can be report
96. rnally as a true differential offset voltage The voltage is also available to be used externally through a rear panel connector To maintain the amplifier s high Common Mode Rejection performance special differential probes such as the Teledyne LeCroy model DXC series are recommended and are available as optional accessories DA1855A Differential Amplifier Model Description The DA1855A series is comprised of 2 models which differ in physical configuration Both contain the same 100 MHz differential amplifier which provides high common mode rejection extremely fast overdrive recovery selectable 1 or 10 attenuation selectable X1 or X10 gain a 5 1 2 digit Precision Voltage Generator PVG selectable upper bandwidth limiting filters an effective gain display and 500 mV output swing limiting The PVG is provides a calibrated reference for Differential Offset or Comparison modes The PVG reference voltage is also available through a BNC connector on the rear panel DA1855A Single channel unit packaged in a convenient desk top housing DA1855A PR2 Two independent model DA1855A amplifiers packaged in one housing with one line power input connection The housing is intended for desk top use where it can be placed under an oscilloscope Rack Mount Versions Rack mounted versions available for models e DA1855A RM Single channel rack mounted version e DA1855A PR2 RM Dual channel rack mounted version Power Cable Option O
97. s the calculated rise time Record the result as Calculated Rise Time at X1 Gain in the Test Record 5 Check High Frequency CMRR NOTE Common Mode Rejection Ratio CMRR is defined as the Differential Mode Gain divided by the Common Mode Gain normalized inverse of the Common Mode Feedthrough At higher frequencies gt 10 MHz where the bandwidth of the amplifier begins to attenuate the differential mode signal both the differential mode gain and common mode gain feedthrough must be measured to derive the CMRR a Make the set up the same as used for the bandwidth test Steps 4 a e See Figure 17 Oscilloscope DA1855A Leveled Sine Wave Generator Front eae po ooo po Sanan E Standard 500 Attenuator kel Set Input Coupling to DC 500 Figure 17 X1 and X10 HF CMRR Check Setup b Set the DA1855A GAIN to X1 ATTENUATOR to 1 69 DA1855A Differential Amplifier c Set the leveled sine wave generator output frequency to 50 kHz If necessary adjust the output amplitude for a display of exactly 6 divisions 300 mV peak to peak d Change the output frequency to 10 MHz taking care not to change the output amplitude e Measure the peak to peak output amplitude of the DA1855A Record the reading to two digit resolution xx0 mV as Amplifier Output Voltage at 10 MHz in the Test Record f Divide the measured output amplitude by 300 mV Record the answer to two digit resol
98. serial number Provide your name and contact number and if possible describe the defect or failure In case of products returned to the factory a Return Authorization Number RAN must be used Contact your nearest Teledyne LeCroy office or the New York Customer Care Center to receive a RAN Return shipment should be prepaid Teledyne LeCroy cannot accept COD or Collect Return shipments We recommend air freighting 1 Contact your local Teledyne LeCroy sales or service representative to obtain a Return Authorization Number Remove all accessories from the probe Do not include the manual Pack the probe in its case surrounded by the original packing material or equivalent and box Label the case with a tag containing e The RAN e Name and address of the owner e Probe model and serial number e Description of failure Package the probe case in a cardboard shipping box with adequate padding to avoid damage in transit Mark the outside of the box with the shipping address given to you by the Teledyne LeCroy representative be sure to add the following e ATTN lt RAN assigned by the Teledyne LeCroy representative gt e FRAGILE Insure the item for the replacement cost of the probe If returning a probe to a different country also e Mark shipment returned for service as a Return of US manufactured goods for warranty repair recalibration e If there is a cost involved in the service put the service cost in the value
99. sh button which decrements the corresponding digit The button above the left most digit changes the PVG output polarity The ZERO button below the left most digit sets the output to zero and invokes the PVG s Auto Zero function PVG absolute mode DA1855 PVG increment and decrement buttons always function to increment or decrement the voltage display respectively When decrementing from a positive voltage the display always stops at zero To obtain negative voltages the button must be pushed and the increment button is used to increase the magnitude of the negative voltage This operation is natural if simply setting a voltage but unnatural if moving a displayed oscilloscope waveform This is known as the PVG absolute mode and the only mode available in the original DA1855 non A model The DA1855A retains the option of operating in this same manner as well as supporting PVG roll through zero mode NOTE When the DA1855A is controlled remotely through a Teledyne LeCroy oscilloscope neither PVG absolute or PVG roll through zero modes apply When operated remotely the PVG value is controlled with the use of the OFFSET knob on the oscilloscope when in effect operates in the roll through mode PVG roll through zero mode The DA1855A increment buttons are oscilloscope waveform related by factory default The increment buttons move a displayed oscilloscope waveform upward and the decrement buttons move the waveform downward independe
100. ssive networks which divide each signal by ten In 1 mode the front panel input connectors are directly connected to the DA1855A ampilifier s differential inputs In 10 mode each front panel input connector is connected to a passive 1 MQ attenuator The attenuator output is connected to the DA1855A amplifier s corresponding differential input The signal at each input is attenuated by a factor of ten Gain The DA1855A amplifier gain amplification is selectable between X1 and X10 The amplified signal appears at the rear panel AMPLIFIER OUTPUT connector Gain will affect the differential mode output signal by amplifying the signal difference between the INPUT and the INPUT but will not affect the common mode signal the signal common to the INPUT and them INPUT Output Termination Proper gain is obtained when the DA1855A drives a 50 Q load such as an oscilloscope with input impedance set to 50 Q Automatic 50 Q termination is obtained when the DA1855A is connected to a Teledyne LeCroy oscilloscope through the ProBus interface An instrument with only a 1 MO input impedance available should have a 50 Q coaxial termination placed on its input connector The DA1855A is then connected to the oscilloscope through the coaxial termination Input Resistance When the input ATTENUATOR is set to 1 and no attenuating probe is connected the input resistance can be increased from 1 MQ to 100 MQ This is advantageous when measuring high i
101. stance of both inputs PRx PROBEATTENUATION Reports the attenuation of the passive probe attached to the amplifier PRx PVGMODE Selects the Precision Voltage Generator Offset mode PRx VDIV Selects the vertical scale factor of the probe amplifier oscilloscope system 46 Operator s Manual Gain Control Mode The DA1855A amplifiers have two modes for setting the amplifier gain and attenuation Auto and Manual Refer to Gain Control Modes on page 47 Operation for more information The gain control mode can be selected in the DA1855A control menu through the oscilloscope front panel or through remote control by sending the commands which correspond tot the gain mode Sending the PRx ATT control mode EN or PRX GAIN commands will set the DA1855A amplifier to Manual gain Sending the PRx VDIV command will set the DA1855A amplifier to Auto gain control mode Attenuation Description Command Syntax Query Syntax Response Format Example PRx ATTENUATION PRx ATTEN Command Query The PRx ATTENUATION command sets the attenuation of the differential amplifier including the factor of any passive probe attached to the input The command will also switch the Atten Gain control mode to Manual if it was to Auto mode The valid arguments with no probe attached is 1 or 10 when the input resistance is set 1 MQ or only 1 when the input resistance is set to 100 MQ The valid arguments must be scaled by
102. such as clipping or bandwidth limiting e Limitation in the acquisition process such as sample rate resolution and record length e Limitation in the computational algorithms The most common source of error in power measurements results from the time delay skew between the voltage and current waveforms The propagation delay through the current probe and the voltage probe plus differential amplifier are almost never equal To eliminate resulting error in power waveforms it is necessary to deskew the input signals Some oscilloscopes have a deskew function that can be used to shift the time reference of one of the waveforms relative to the other Another error to be concerned with is the phase shift in the probes or instrument As the rise time of the input signal approaches the rise time of the current probe or amplifier the phase shift will create an amplitude error in the power waveform 45 DA1855A Differential Amplifier Remote Control Commands When attached to a Teledyne LeCroy oscilloscope equipped with ProBus interface the DA1855A Amplifier can be remotely controlled along with the other oscilloscope functions The control interface can be either the RS 232 or IEEE 488 GPIB bus The commands which control the amplifier are described below The text for the command descriptions is formatted in a style consistent with the oscilloscope command descriptions contained in the Teledyne LeCroy Digital Oscilloscopes Remote Control Manua
103. the oscilloscope spectrum analyzer or digitizer Frequency response and transient response are essentially independent of the oscilloscope s input impedance 20 MHz A 20MHz three pole 18dB octave filter allows the DA1855A to reduce extraneous noise This filter is a passive LC design and is intended to drive a 16 Operator s Manual 50 Q load Without the load the filter s frequency response and transient response are altered 1 MHz The 1M filter is of the same design as the 20 MHz filter and the same remarks apply 100 kHz The 100kt z filter is an active filter with a 50 Q output impedance Transient and frequency response are independent of the load impedance Overload When a signal which could damage the DA1855A has been applied to either input connector the DA1855A protects itself by disconnecting the signal The input coupling mode changes to OFF and the OVERLOAD light is turned on To reset the amplifier to normal operation remove the offending input press any of the input coupling modes AC OFF or DC The Overload light will turn off indicating the amplifier is reset When the ATTENUATOR is set to 1 an input signal of approximately 19 Volt will activate the overload protection circuit Fast transients will draw up to about 70 mA of input current for a brief period before the input coupling relay acts to disconnect the input AN CAUTION Inputs in excess of 250 Volt may cause permanent damage to the DA1855A
104. the attenuation factor of any passive probe which is attached to the amplifier The PRx ATTENUATION query returns the attenuation of the differential amplifier including the attached probe connected to the specified channel lt channel gt ATTeNuation lt attenuation gt lt channel gt PRI1 PR2 PR3 PR4 lt channel gt 1 10 when input resistance is set to1MQ or 1 when the input resistance is set to 100 MQ Attenuation arguments must be scaled by the attenuation of any passive probe which is attached to the differential amplifier inputs lt channel gt ATTeNuation lt channel gt ATTN lt attenuation gt The following command sets the attenuation of the differential amplifier connected to channel 1 to 100 when a 10 probe is attached CMDS PR1 ATTN 100 CALL IBWRT SCOPE CMDS 47 DA1855A Differential Amplifier Auto Zero Description Command Syntax Example PRx AUTOZERO PRx AZ Command The PRx AUTOZERO command initiates an auto zero cycle of the differential amplifier to remove any offset drift from the output The amplifier inputs will be disabled for a fraction of a second during the autozero cycle lt channel gt AutoZero lt channel gt PR1 PR2 PR3 PR4 The following command initiates an auto zero in the DA1855A Differential Probe attached to channel 1 CMDS PR1 AZ CALL IBWRT SCOPE CMDS Bandwidth Limit
105. the voltage which is used in the Vcomp and Vpirr modes and appears at the rear panel OFFSET VOLTAGE PVG output connector for use as a reference voltage The Precision Voltage Generator PVG output range is 15 500 Volt The PVG is never attenuated by the input attenuator Attenuation of the INPUT signal by the 10 input attenuator will cause the PVG to null out an input voltage up to 155 00 Volt which is ten times larger than the actual PVG voltage The increase in common mode voltage range also applies when using attenuating probes 14 Operator s Manual When the DA1855A is used with attenuating probes that feature readout the PVG display is changed to indicate the voltage at the INPUT probe tip which will bring the amplifier output to zero When connected to a Teledyne LeCroy oscilloscope via the ProBus interface the oscilloscope OFFSET control increments or decrements the PVG s output voltage and the offset value will be shown on the six PVG front panel indicators The new offset value will also be displayed on the oscilloscope s screen for a few seconds after a change has been made When connected to an oscilloscope not provided with a ProBus interface the PVG can be accessed by means of push buttons Above each digit is a push button which increments the corresponding digit by one when pushed When held the digit continues to increment eventually incrementing the next higher digit Similarly below each digit is a pu
106. tial amplifier is operating in an environment with stable ambient temperature KR Voltages are referred to the amplifier input connector Multiply by probe attenuation factor to obtain value refer to probe input e g 0 1 50 uV becomes 0 1 500 uV at the probe tip when using a 10 probe DA1855A Differential Amplifier Physical Characteristics Height Width Depth Weight Shipping Weight DA1855A DA1855A PR2 DA1855A DA1855A PR2 DA1855A DA1855A PR2 DA1855A DA1855A PR2 DA1855A DA1855A PR2 7 29 cm 2 87 inch 8 75 cm 3 4 inch 21 2 cm 8 36 inch 43 9 cm 17 3 inch 23 2 cm 9 12 inch 42 5 cm 16 7 inch 2 15 kg 4 lbs 12 oz 9 5 kg 21 Ibs 3 12 kg 6 lbs 14 oz 11 3 kg 25 Ibs Operator s Manual Overview The DA1855A is a stand alone high performance 100 MHz differential amplifier It is intended to act as signal conditioning preamplifier for oscilloscopes spectrum analyzers and other instruments providing differential measurement capability to instruments having only a single ended input When used with a DA1855A high quality oscilloscopes can obtain common mode rejection and overdrive recovery performance that was previously unobtainable in any product When used with a Teledyne LeCroy oscilloscope equipped with ProBus interface the DA1855A can be controlled through the oscilloscope user interface or remote commands When used with non ProBus oscilloscopes the DA1855A settings can
107. to 5 mV div with DA1855A set at X10 GAIN and time div adjusted for 2 to 3 cycles Under these conditions the display on the oscilloscope will extend off the top and bottom of the screen 31 DA1855A Differential Amplifier Press the INPUT s Vcomp button This internally applies the Precision Voltage Generator s output to the DA1855A s INPUT and the OFF light goes out the INPUT connector is disabled The positive and negative peaks of the waveform displayed on the oscilloscope are respectively 10 divisions above and below the display center line Push the button above the digit that is two places right of the decimal 10 mV in the Precision Voltage Generator PVG until the positive peak of the waveform appears in the oscilloscope s display Continue incrementing and decrementing Precision Voltage Generator s digits until the peak of the waveform is at the centerline of the oscilloscope s display The number in the Precision Voltage Generator display is the waveform s positive peak voltage Press the button in the Precision Voltage Generator Observe that the negative peak of the signal is now at or near the oscilloscope s display centerline By incrementing and decrementing the digits the negative peak can be positioned to the oscilloscope s display centerline At this point the number in the Precision Voltage Generator s display is the waveform s negative peak voltage Change the oscilloscope s sensitivity
108. u are required to follow generally accepted safety procedures in addition to the precautions specified in this section The overall safety of any system incorporating this accessory is the responsibility of the assembler of the system Symbols These symbols appear on the instrument s front or rear panels and in its documentation to alert you to important safety considerations CAUTION of potential damage to instrument or WARNING of potential bodily injury Attend to the accompanying information to protect against personal injury or damage Do not proceed until conditions are fully understood and met High voltage Risk of electric shock Measurement ground connection Safety protective ground connection Alternating Current Power On connected to AC mains Power Off disconnected from AC mains O He E Precautions e Use proper power cord Use only the power cord shipped with this instrument and certified for the country of use e Maintain ground This product is grounded through the power cord grounding conductor To avoid electric shock connect only to a grounded mating outlet e Connect and disconnect properly Do not connect disconnect probes or test leads while they are connected to a voltage source e Observe all terminal ratings Do not apply a voltage to any input that exceeds the maximum rating of that input Refer to the specifications for maximum input ratings e Use only within operational environment list
109. ution 0 xx in the Test record This is the Differential Mode Gain at 10 MHz g Remove the leveled sine wave generator from the INPUT of the DA1855A h Connect a BNC cable from the Frequency Reference Signal Output of the sine wave generator to the External Trigger Input of the oscilloscope If the sine wave generator does not have a Frequency Reference Signal Output insert a BNC Tee adapter into the Output connector and attach the External Trigger BNC cable to the BNC Tee i Disconnect the AMPLIFIER OUTPUT cable from the oscilloscope s channel 1 and connect the terminated end of the sine wave generator output cable to the channel 1 input of the oscilloscope Refer to Figure 18 Oscilloscope Set Input Coupling RSC Standard a 502 Terminator External Trigger Input Frequency Reference Output Generator io lott o Figure 18 HF CMRR Check Setup j Verify that the channel 1 input coupling is set to DC and 1MQ 70 Operator s Manual Set the oscilloscope to display channel 1 the vertical sensitivity to 5 00mV div timebase to 50 ns div and trigger source to external 10 If necessary adjust the trigger level for a stable display Set the leveled sine wave generator frequency to 10 MHz Set the leveled sine wave generator output amplitude to exactly 2 Vp p 4 divisions on the oscilloscope Remove the leveled sine wave generator output cable and ter
110. y Korea 10th fl 333 Yeongdong daero Gangnam gu Seoul 135 280 Korea teledynelecroy com korea Ph 82 2 3452 0400 FAX 82 2 3452 0490 Japan Teledyne LeCroy Japan 3F Houbunshafuchu Bldg 3 11 5 Midori cho Fuchu Shi Tokyo 183 0006 Japan teledynelecroy com japan Ph 81 42 402 9400 FAX 81 42 402 9586 For a complete list of offices by country including our sales amp distribution partners visit teledynelecroy com support contact Operator s Manual Warranty Teledyne LeCroy warrants this oscilloscope accessory for normal use and operation within specification for a period of one year from the date of shipment Spare parts replacement parts and repairs are warranted for 90 days In exercising its warranty Teledyne LeCroy at its option will either repair or replace any assembly returned within its warranty period to the Customer Service Department or an authorized service center However this will be done only if the product is determined by Teledyne LeCroy s examination to be defective due to workmanship or materials and the defect is not caused by misuse neglect accident abnormal conditions of operation or damage resulting from attempted repair or modifications by a non authorized service facility The customer will be responsible for the transportation and insurance charges for the return of products to the service facility Teledyne LeCroy will return all products under warranty with transportatio

DA1855A Differential Amplifier Operator`s Manual

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