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TBX-1325 High-Voltage Terminal Block Installation Guide

1. Manual For information regarding the function and use of the SCXI 1124 signals consult your SCXI 1124 User Manual Read the next section Voltage Drops before proceeding with the signal connections Voltage Drops The voltage output of the SCXI 1124 can drive up to 5 mA When you use the SCX I 1124 in voltage mode with the TBX 1325 a small amount of voltage drop will develop across the positive negative channel wires in the SH48 48 A cable and across any other wires you may have connected to this channel This voltage drop is due to the wire resistance and the current flow in these leads Voltage drop is not a concern if you are using the SCXI 1124 in the current mode To reduce errors in your output voltage first you need to calculate the voltage drop across the SH48 48 A cable This voltage drop results in an error in your measurement and depends on the cable length and on the load impedance and configuration Solutions to this problem include e Locate the load closer to the SCXI 1124 by using shorter cable lengths e Use heavy gauge wire to connect to the TBX 1325 e Add a high impedance input buffer near the load e Calibrate your system to account for the resistive losses of the cable The SH48 48 A cable has a resistance of 0 21 Q m To determine the amount of error introduced by the cable do the following 1 Calculate the total resistance R of the cable based on the cable length 2 Determine the amount of current I bein
2. 3 SH48 48 A Cable Figure 3 Connecting the SH48 48 A Cable to the SCXI Module 13 Connect the other end of the cable assembly to your TBX 1325 terminal block connector and secure the SH48 48 A cable by tightening both backshell mounting screws See Figure 4 See Figure 5 for the completed installation 1 Backshell Mounting Screws and Ears 3 Captive Cover Screws 5 Signal Wire Entry 2 Shield Grounding Solder Lugs 4 Terminal Block Connector Note The SH48 48 A cable is not shown in the exact position for proper connection to the terminal block connector See Figure 5 for the completed connection Figure 4 Connecting the SH48 48 A Cable to the TBX 1325 Terminal Block Figure 5 The Completed Installation Rack Mounting Once you have completed the above installation instructions you are ready to mount the TBX assembly in your rack If you are using the National Instruments TBX Rack Mount Assembly refer to the TBX Rack Mount Installation Guide for instructions If you are not using this rack mount assembly perform the following steps to mount the TBX assembly directly onto your DIN rail 1 Snap the TBX terminal block onto the DIN rail with a firm push To remove the TBX terminal block from the DIN rail place a flathead screwdriver into the slot above the terminal block base and pry it from the rail 2 Install the SCXI chassis using the appropriate chassis rack mount kit Signal Connection Th
3. INSTRUMENTS The Software is the Instrument Pitcrrume Installation Guide TBX 1325 High Voltage Terminal Block This guide describes how to install and use the TBX 1325 high voltage terminal block with the SCXI 1124 module Introduction The TBX 1325 high voltage terminal block is a DIN rail mountable terminal block with 30 screw terminals for easy connection to the SCXI 1124 front connector Six of the screw terminals connect to the SCXI chassis ground via the SH48 48 A cable The remaining 24 screw terminals are for signal connection to the six module output channels The TBX 1325 mounts on most European standard DIN EN mounting rails What You Need to Get Started LJ TBX 1325 high voltage terminal block kit TBX 1325 high voltage terminal block TBX 1325 High Voltage Terminal Block Installation Guide s in flathead screwdriver SCXI chassis SCXI 1124 module and documentation SH48 48 A cable assembly Long nose pliers 346 in Wrench D O O O O L No 1 Phillips head screwdriver Product and company names are trademarks or trade names of their respective companies 371202A 01 1996 National Instruments Corporation All rights reserved March 1996 Installation Perform the following steps to mount the SH48 48 A cable assembly and connect the TBX 1325 to your SCXI 1124 module Refer to Figures 1 and 2 as needed Warning SHOCK HAZARD Refer to the Signal Connection section BEFORE connecting signals If signal wires a
4. e following warnings contain important safety information concerning the use of hazardous voltage levels with TB X 1325 terminal blocks Warnings SHOCK HAZARD Only qualified personnel aware of the dangers involved should use the TBX 1325 If signal wires are connected to the terminal block dangerous voltage levels may exist even when the equipment is turned off Before you remove or work with any installed terminal block disconnect the AC power line or any high voltage sources gt 30 Vrms and 42 4 V peak or 60 VDC that may be connected to the terminal block National Instruments is NOT liable for any damages or injuries due to misuse of high voltage signals connected to the terminal block When using the terminal block with high voltage levels you must insulate all signal wires appropriately to the highest voltage the terminal block may come in contact with National Instruments is NOT liable for any damages or injuries resulting from inadequate signal wire insulation Any CHASSIS GROUND terminal on your terminal block is for grounding high impedance sources such as a floating source 1 mA maximum Do not use these terminals as safety earth grounds Operating common mode voltage must not exceed 250 Vrms between banks or from any bank to earth When connecting your field signals to the TBX 1325 high voltage terminal block for use with the SCXI 1124 follow the labeling on the TBX 1325 that matches the signal names from the SCXI 1124 User
5. g drawn from the SCXI 1124 3 Use the following formula to determine the total voltage drop V channel leads drop IN the positive negative V cop Rn X L For example if you have a 1 m SH48 48 A cable and a 5 mA load then your calculations from steps 1 through 3 would be 1 Ra 2x 0 21 QO mx 1m 0 42 Q notice that you multiply the cable length by 2 to take into consideration both the positive and negative channel lead resistances 2 L 5 mA which is the total current draw from the SCXI 1124 3 Vap 2 1 mV lt 0 042 of full scale at 0 to 5 V range drop You then need to calculate the voltage drop across the field signal wires you are connecting to the TBX 1325 For example 30 m of 22 AWG stranded copper wire has about 1 5 Q of resistance Thus driving a load 15 m away at 5 mA will produce an error at the load of 7 5 mV Add this error amount to the voltage drop across the SH48 48 A cable to get a total voltage drop of 9 6 mV Wiring Instructions To connect your field signals to the TBX 1325 terminal block refer to Figures 4 and 6 as you perform the following instructions 1 Remove the TBX 1325 terminal block cover by unscrewing the four captive cover screws in the cover corners These screws stay attached to the cover without falling out 2 Connect the signal wires to the screw terminals Refer to your SCXI module user manual for examples of how to connect to field signals and loads Note The board has corre
6. re connected to the terminal block dangerous voltages may exist even when the equipment is turned off 1 Turn off your SCXI chassis 2 Turn off the computer that contains your data acquisition device or disconnect the device from your SCXI chassis 3 Slide the SCXI module out of the SCXI chassis 4 Unscrew the SCXI module grounding screw with a No 1 Phillips head screwdriver and remove the module cover see Figure 1 Grounding Screw Figure 1 Removing the SCXI Module Cover 5 Place one jack screw as shown in Figure 2 6 While holding the jack screw in place insert the lockwasher and then the nut Use long nose pliers to do this 7 Tighten the nut by holding it firmly and rotating the jack screw with a 3 6 in wrench 8 Repeat steps 5 through 7 for the second jack screw 9 Replace the SCXI module cover and tighten the grounding screw 1 Grounding Screw 3 Lock Washers 2 Nuts 4 Jack Screws Figure 2 Preparing the SCXI Module for the Cable Assembly 10 Slide the SCXI module back into place in the SCXI chassis 11 Verify that the backshell mounting ears are in the position shown in Figure 3 If not remove the backshell mounting ears and install them in the position shown 12 Connect one end of the cable assembly to your SCXI module front connector and secure the SH48 48 A cable by tightening both backshell mounting screws 1 Backshell Mounting Screw 2 _ Backshell Mounting Ear
7. sponding rows labeled A and B to help you make the correct connections as shown in Figure 6 item 2 Note that the CHASSIS GROUND terminals are connected to the SCXI chassis via the cable shield This is not shown in your SCXI module user manual Allow your signal wires to exit through the terminal block cover opening Note This terminal block does not provide strain relief for field signal wires Add strain relief insulation and padding for your field signal wires if necessary 3 Replace the TBX 1325 terminal block cover and tighten the captive cover screws The installation and signal connection are now complete Figure 6 shows the TBX 1325 parts locator diagram ToK ro o o O ja io O HIGH VOLTAGE NATIONAL FiNsTRUMENTS g 1996 T B xX _ 1 3 2 5 ASSY183181B 01 J4 AS J y o 0 0 OJO O 0 o Oo O O Oo A A A A CHASSIS GROU annga9o SISSVHO NIST LN NIST LN NIST LA NIST LN Co y pi D oo o Adans AA o Adans W T K mo pe gt es AL ser 1 Cover Mounting Nuts 4 Backshell Mounting Nut 7 Serial Number 2 Corresponding Rows 5 Cable Mating Connector 8 Assembly Number 3 Product Name 6 Signal Wire Screw Terminals 9 Chassis Ground Screw Terminal Figure 6 TBX 1325 Parts Loca
8. tor Diagram Specifications Common mode isolation 250 Vrms between channels and channel to earth ground Compatible DIN rails eee eeeeeeeeseeeetees DIN EN 50 022 DIN EN 50 035 Terminal block dimensions cceeeeeees 12 7 x 7 62 x 11 18 cm 5 x 3 x 4 4 in

TBX-1325 High-Voltage Terminal Block Installation Guide

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