MEASUREMENT TECHNOLOGY
Contents
1. UTERBACH HESSEN PHONE 49 66 416610 FAX 49 664166133 E MAIL lauterbach schramm gmbh de INTERNET http www schramm gmbh de compensation cables for thermocouples are not necessary When using the transmitter please take notice of the following The contents of these instructions or the operating manual provided with the transmitter The relevant rules involving the installation and operation of electrical systems in some cases the regulations and directives for explosion protection 5 Mounting and Operation 5 1 Installation The thermometer thermocouple resistance thermometer must be brought into contact with the medium to be measured in the best possible manner To avoid thermal conduc tion errors the immersion depth should be 6 8 times greater in fluids 10 15 times greater in gases than the protective tube diameter The tem perature sensitive length should be 1 to 1 5 times greater than the resistance elements or 30 50 mm by an o d of 6 mm If only very short installation lengths are possible the temperature sensitive length of a resistance element or 30 50 mm may not be undershot by 1 to 1 5 times when applying either ther mocouples or resistance thermometers It is often helpful to install a pipe bend whereby the protective tube must be positioned against the flow of the medium 5 2 Connecting wires For all connecting wires it is important to ensure that proper contact has been estab lished an2. a eh j ee y t ZIE C User Manual for Resistance Thermometers and Thermocouples 1 General We supply complete thermometer assemblies ready for immediate use These thermocou ples or resistance thermometers are sensitive devices which contain either glass or ceramic parts They must therefore be handled with due care On receiving the thermometer assembly carefully unpack all supplied articles including those that may be deliver ed in dismantled form Long thermometers must be supported at various points and Lifted up or transported in an appropriate manner The same care must be taken during the actual installation of the device Prior to installation please check the thermometers see 7 1 to ensure that the device has suffered no transportation damages 2 Thermocouples Thermocouple assemblies are delivered with 1 2 or sometimes 3 thermocouple elements The measuring point is usually insulated but can still be connected to the protecting tube The connection of the thermocouple to the measuring instrument is established with a compensation lead CL Only use the speci fied type of compensation lead and the appropriate polarity for connection of thermo couple The leads should be at least 0 5 m away from the power cables preferably laid in their own cable trays Twisted and shielded cables suppress magnetic and electrical parasitical interferences 3 Resistance Thermometers Resistance thermometer
3. d Typical Resistance thermometer faults Fault Probable or possible cause Remedy Too high or fluctuating temperature readout despite known cross section accurate sensor of the resistance thermometer wire resistance too high uncompensated supply lead resistance altered by high temperature if still possible select 2 wire leads with bigger cross sections eventually move to a more accessible point and shorten wire lead adjustment change 3 or 4 wire system use the head transmitter Fluctuating temperature readout even though measuring circuit of the resistance thermometer Voltage or power supply is not constant must be kept constant at lt 0 1 Fully affects the measurement when tuned off bridge and current voltage measurements 4 wire Our information regarding our prod ucts equipment plants and processes is based on extenvise development and experience in the field of applied engineering This information is made available to the best of our knowledge and in written form without assuming any liability over and above the terms of this contract but reserving the right to make technical changes to our pro ducts at any time without prior notifica tion In addition our applications engineers are available on request to provide further consultation and co operation in solving production and application related problems This however does not relieve the user from ob
4. d that corrosion humidity pollution electrical parasitic interferences of power cables etc are avoided The cables should be insulated to counter the ambient influences dry humid chemicals aggressive influences heat whereby the ambient tem perature of both the cable and the connection head may not exceed 100 C Please pay attention to the valid standards and regula tions when selecting the types of cables to be used If possible all measuring systems should be operated in ungrounded condi tions or only grounded at one point When using thermocouples connected to protective tubes these should be the only ground mass connection 5 3 Protection Tubes Thermometers can be installed in any mount ing position preferably hanging vertically up to temperatures reaching apprx 500 C Ceramic protection tubes must be protected from mechanical stress bumps bends inclu ding temperature shocks e g through direct flame contact If they are applied to hot processes e g when changing the thermo couple they must be either prewarmed or inserted very slowly 1 2 cm min at 1600 C 10 20 cm min at 1200 C This also applies when removing the hot protecting tube Care must be taken to avoid suspending lengths gt 500 mm for temperatures gt 1200 C 5 4 Instructions for explosion proof components Maintenance work repairs may be con ducted only under the following conditions and must follow legal guidelines or regula
5. eters to between 200 and 400 C without temperature control gives fur ther clues to interruptions polarity errors for thermocouples and low insulation resistance etc The accuracy of thermometers acc to 7 Troubleshooting ISO 9000 can only be checked by a reference 7 1 Quick Check of thermocouples and resistance thermo meters including their associated measuring order if R lt 20 Ohm wire gt 0 5 mm the value depends on the wire cross section and the length Risol 100 MOhm for insul ated thermocouples 7 2 Error Table for Thermocouples and Resistance Thermometers element Therefore in most cases the thermometers have to be removed and checked by a heating device The entire temperature measuring circuit should be routinely checked The following table contains an illustration of the most important errors and provides suggestions towards their solution Fault Probable or possible cause Remedy Errors in the measuring signal a electrical magnetic pick up at least 0 5 m spacing between the measuring cable and power cables supply lines if laid parallel electrostatic shielding caused by a metal foil braiding grounded at one point twist the core wires in pairs to combat magnetic pick up right angled crossing of electrode with interfering power cables b Grounded loops only one grounding point in circuit or floating measuring system ungrounded c Drop in insulation
6. ligation to verify the suitability of our information and recommendations before putting our products to use This applies particularly to deliveries destined for customers in foreign coun tries especially in their obligation to ensure that no patent rights of third parties are infringed upon including applications and processing methods which we have not expressly spelled out in writing In case of damage or quality deficiencies our liabilities and indemnities are limited to the same volume as stipulated in our General Terms of Supply and Delivery 07 2009 THERMOCOUPLE COLOR CODE oe Pt13Rh Pt Pt30Rh Pt6Rh white white red orange red black oe int eee white red RESISTANCE TEMPERATURE DETECTOR COLOR CODE 1 x Pt100 2xPt100 Colour in brackets for Type MWO8 and MWO8 Ex 07 2009
7. nsertion length change the measuring point if poss special construction of inset and protecting tube Highly corroded protecting tube composition of the medium is not as assumed or has changed unsuitable material chosen for protecting tube check the medium eventually analyze the defective protecting tube and select a more suitable material while providing additional surface protection in certain circumstances the protecting tube must be replaced from time to time since it is subject to wear TSL Temperature Sensitive Length 07 2009 Typical Thermocouple faults a 7 ty oee Peai k Fault Probable or possible cause Remedy Fluctuating temperature readout even though thermocouple circuit is faultless Reference junction temperature or voltage is not constant temperature or supply voltage must be kept constant at lt 0 1 check instruments for non precious metal thermocouples use the full value for measurement use only about half the value for thermocouples made of precious metals Temperature display highly deviates from the table values for thermocouples improper material combinations bad electrical contacts parasitic voltages thermostatic voltages galvanic voltage wrong compensation cable check thermocouples and wires for correct pairing correct compensation lead correct pinup permitted ambient temperature at connection hea
8. resistance humidity has eventually penetrated the thermometer insert in this case dry and rescale replace insert check to see if thermometer is thermally overloaded Fault Probable or possible cause Remedy Response times too long incorrect readouts a wrong location for installation there is a heat source within the flow path change the point of installation so that the medium can transmit its temperature to the thermometer without interface b wrong installation insufficient installation depth excessive loss of warmth immersion depth approx TSL 6 x fluids up to 10 x gases d d external protecting tube ensure for thermal contacts especially on the surface measurements are established with matching contact surfaces and or heat conducting materials c protecting tube too thick drilled hole for protecting tube too big select the smallest possible protecting tube for this process response time at first exposure should be proportional to the cross section or the volume of the thermometer depending on the tentative thermal figures and air gaps within the assembly fill any such gaps with contact agent oil grease if possible d Deposits on the protecting tube remove during inspections if possible select another protecting tube another installation point Thermometer interruptions Vibrations reienforced springs on insert shorten insert i
9. s are supplied with 1 2 or sometimes with 3 measuring resistors The measuring point is isolated The connec tion between resistance thermometer and measuring instrument is mostly a 2 wire type the sum and compensation of line resistance become part of the measurement To obtain accurate measurements 3 wire technique is used If highly accurate measurements are desired the 4 wire technique with constant current and high resistance voltage pick up are used Conventional copper cables usually found on the market preferably with 1 5 mm2 cross section should be laid if possible at about 0 5 m away from the power cables preferably on their own cabletrays Twisted and shielded cables suppress magnetic and electrical parasitical interferences Depending on the type care must be taken not to exceed the measuring currents of 0 1 to 10mA recommended by the manufacturer errors may result from inherent heating 4 Thermometer with Head Mounted Transmitter The afore mentioned problems which could eventually be caused by transfer resistances in the cable and EMC can be prevented by installing a 2 wire transmitter output signal 4 20 mA in the sensor head Only a 2 core copper cable is required Multiple wire circuits for resistance thermometers and SALES and ADMINISTRATION FLINSCHSTRASSE 18a 60388 FRANKFURT AM MAIN PHONE 4969 420070 FAX 49 69 42007 26 E MAIL firma schramm gmbh de PRODUCTION ALTEBERGSTRASSE 44 36341 LA
10. tions 1 Repair work may only be carried out using original components of the original manu facturer otherwise the standards stipulated in the Certificate of Conformity shall not be fulfilled 2 When ordering spare parts exact infor mation on previous delivery such as type of protection Exd Exi Certificate of Conformity number serial and item No s must be supplied 3 Ex protected thermometers only fulfil the required safety requirements as a unit component as determined by the Certificate of Conformity Measuring insets or connecting heads alone do not satisfy the explosion protection requirements 4 If SCHRAMM supplies thermometers destined for operation in hazardous areas ordered without protecting tubes it is the responsibility of the buyer to ensure 4 1 that these thermometers are deployed only in zones which are permissible in accordance with the Certificate of Conformity or with the manufacturer s declaration e g Zones 1 or 2 4 2 a protecting tube is provided in the event of an obligatory zone seperation e g from Zone 0 from Zone 1 Such a tube must correspond fully to the special con ditions spelled out in the respective Certificate of Conformity 5 SCHRAMM shall advise the plant manager regarding 4 1 and 4 2 as maintained above 6 Maintenance The thermometer and the entire temperature measuring circuit must be checked at regular intervals for wear and tear of protecting
11. tube or chemical activity drifts of the measuring element caused by aging reduction of insulation resistance through humidity and pollution improper contact of the wire connections mechanical and chemical damage of the thermometer and wires Resistance themo meter circuits can be checked by replacing the measuring element with a known defined resistance thereby simulating a specific temperature Thermoelement measuring circuits can be checked by connecting a mV voltage of a known v 07 2009 ariable to the measuring circuits instead of the thermocouple In both cases substan tial deviations from the set point can be determined and also if the thermometer or the instrumentation is the cause of functio nal errors The insulation resistance of the entire ungrounded measuring circuit wires and thermometer against ground should be gt 1 MOhm measured with 100V DC circuits in dismantled form Required instru ments mV meter Ohm meter or resistance bridge insulation meter with 60 100 V vol tage all measurements at room temperature in the case of room temperature the throughput and insulation are checked by knocking to see if any wire breaks have occured a thermocouple is regarded as being in ae t pa Ni A aresistance thermometer is considered to be in order if R is about 100 Ohm for Pt 100 Risol gt 100MOhm A heating up of the thermocouples or resi stance thermom
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