Omega Thermometer TX91 User Manual

Users Guide  
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and reserves the right to alter specifications without notice.  
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3.Repair instructions and/or specific problems relative to the  
product.  
FOR NON-WARRANTY REPAIRS, consult OMEGA  
for current repair charges. Have the following  
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product.  
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TABLE OF  
CONTENTS  
TX91  
Miniature Two-Wire Thermocouple Transmitter  
Page  
1
Section 1 Introduction  
1.1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
1
1.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
8
1.3 Models Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
Section 2 Unpacking Instructions  
Section 3 Installation  
8
9
11  
3.1 Mounting the TX91 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10  
3.2 Wiring the TX91 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16  
i
 
TABLE OF  
CONTENTS  
TX91  
Miniature Two-Wire Thermocouple Transmitter  
Page  
18  
Section 4 Calibration Instructions  
4.1 Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
4.2 Set-up of Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19  
4.3 Calibration Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20  
Section 5 Troubleshooting Guide  
Section 6 Accessories  
Section 7 Specifications  
Appendix A  
25  
26  
27  
Intrinsically Safe Interconnection Diagram . . . . . . . . . . . . . . . . . . . . . 30  
ii  
 
Introduction  
1
1.1 General Description  
®
The OMEGA TX90 Series Temperature Transmitters consist of the  
TX91 Miniature Two-Wire Thermocouple Transmitter and the  
TX92 Miniature Two-Wire RTD Transmitter. This manual is written  
for the OMEGA TX91 Thermocouple Transmitter.  
The TX91 Transmitter accepts thermocouple sensor types J, K, T,  
or E and will produce a standard 4-20 mA output signal propor-  
tional to that produced by its attached input temperature sensor.  
Transmission of the proportional current output may be  
accomplished by using copper wires.  
1
 
Introduction  
1
(For Mounting)  
Figure 1-1. Photo of TX90 Series Transmitter  
12  
Figure 1-2. General Dimensions (in inches)  
 
1
Introduction  
The TX91 transmitter is normally powered by an unregulated DC  
power supply as shown in Figure 1-3. The proportionally-transmit-  
ted signal begins at 4 mA, at the low end of its temperature range,  
and increases to 20 mA, at the high end of its temperature range.  
(There are various temperature ranges and thermocouple types  
available for the TX91. To order, refer to Section 1.3 for correct  
Model Numbers and Range Codes.)  
COPPER  
THERMOCOUPLE  
WIRES  
DC SUPPLY  
11-44 VDC  
TX91  
THERMOCOUPLE  
TRANSMITTER  
Input  
3
Figure 1-3. TX91 Thermocouple Transmitter  
 
Introduction  
1
The TX91 two-wire transmitter receives and measures signals from  
thermocouples and sends an output current of 4-20 mA which is directly  
proportional to the thermocouple millivolt input. It is designed to  
connect with only two copper wire leads that will supply the voltage to  
operate the transmitter from a DC power supply, and also carry the  
output current. The output current is then used for recording, computing  
or controlling.  
If the TX91 is mounted inside a protection head, such as the OMEGA  
NB1 Protection Head (see Figure 3-1), the thermocouple extension wires  
are replaced by two copper wires that carry the 4-20 mA signal and DC  
voltage to operate the transmitter. (Refer to the OMEGA Temperature  
Handbook for information on NB1 Thermocouple Assembly.)  
04  
 
Introduction  
1
The TX91 has reverse supply polarity protection and will operate with a  
wide range of supply voltages (11 to 44VDC). It has an input sensor  
break-protection circuit that forces the output current to go upscale when  
the thermocouple wire opens. It also is provided with a screw terminal,  
where the output current can be measured without interrupting the  
power loop. The TX91 does NOT provide isolation between its input and  
the 4-20 mA output; therefore, an undergrounded thermocouple junction  
is suggested to prevent possible ground loops.  
Note that most thermocouple transmitters with 4-20 mA outputs,  
including the TX91, are proportional with respect to the thermocouple  
input voltage. However, the relationship between temperature and  
millivolt for all the thermocouple types is somewhat non-linear. This  
leads to maximum error at approximately the midpoint of the range as  
shown in Figure 1-4.  
05  
 
1
Introduction  
06  
Figure 1-4. Straight line Approximation of Curve  
 
1
Introduction  
1.2 Features  
• 4-20 mA output  
0.1% full-scale accuracy (with respect to the mV input signal)  
• Upscale break protection  
• Low cost  
1.3 Models Available  
Table 1-1. Range Code  
Input Types  
J
Range  
K
T
E
0 to 1200°F  
J2  
J3  
J4  
J5  
J6  
K2  
T2  
T3  
T4  
E2  
-40 to 1300°F  
-40 to 1500°F  
-40 to 1750°F  
-40 to 1000°F  
K3  
K4  
K5  
K6  
E3  
E4  
E5  
E6  
07  
 
1
Introduction  
TX91 Models Available  
Description  
Model Number  
TX91-(*)  
NB1TX-(*)  
Thermocouple transmitter (J, K, T, or E)  
NB1 thermocouple probe, 12" L, /4" O.D.,  
ungrounded junction, 304SS sheath, TX91Transmitter  
1
*Insert range code from Table 1-1  
For complete information on NB1 Thermocouple Probes, see the OMEGA  
Temperature Handbook.  
8
 
Unpacking  
2
Remove the packing list and verify that all equipment has been  
received. If there are any questions about the shipment, please call  
the OMEGA Customer Service Department at 1-800-622-2378 or  
(203) 359-1660.  
Upon receipt of shipment, inspect the container and equipment for  
signs of damage. Take particular note of any evidence of rough  
handling in transit. Immediately report any damage to the ship-  
ping agent.  
NOTE  
The carrier will not honor any claims unless all shipping material is  
saved for their examination. After examining and removing contents,  
save packing material in event reshipment is necessary.  
9
 
Installation  
3
3.1 Mounting the TX91  
The TX91 Transmitter may be:  
1. surface mounted,  
2. mounted inside a protection head (refer to figure 3-1), or  
3. installed into the OMEGA mounting track (part number RT) using an  
OMEGA mounting bracket (part number TX90-BR).  
Figure 3-2 shows the RT mounting track.  
Figure 3-3 shows the TX90-BR mounting bracket.  
Figure 3-4 shows a typical installation of two transmitters using the  
10  
mounting bracket and mounting track.  
 
3
Installation  
DC POWER  
SUPPLY  
LOAD  
MOUNTING  
HOLES  
THERMOCOUPLE  
Figure 3-1 Assembly of the TX91 Transmitter Inside  
an OMEGA NB1 Protection Head (in inches)  
11  
 
Installation  
3
CAUTION  
HANDTIGHTEN  
TRANSMITTER  
MOUNTING  
SCREWS ONLY.  
DO NOT OVER-  
TIGHTEN.  
Figure 3-2 RT Mounting Track (in inches)  
12  
 
3
Installation  
13  
Figure 3-3 TX90-BR Mounting Bracket (in inches)  
 
Installation  
3
MOUNTING TRACK (RT)  
MOUNTING  
BRACKET  
TX90-BR  
Figure 3-4 Installation with Bracket and Track (in inches)  
14  
TX90-BR & RT  
 
Installation  
3
3.2 Wiring the TX91 (Refer to Figure 3-5)  
1. Connect a DC power supply in series with the load to the (+PS) and  
(-PS) power terminals. Note that the load (usually a monitoring  
instrument) may be connected to either the (+) or (-) power lead.  
2. Connect the thermocouple to the (+IN) and (-IN) input terminals.  
NOTE  
A milliamp monitoring instrument can be used in the circuit by  
connecting the monitors positive lead to (+PS) and the negative lead to  
(M). This allows monitoring the current loop without disconnecting the  
15  
main wiring.  
 
Installation  
3
THERMOCOUPLE  
Figure 3-5 Wiring Diagram for the TX91 Potentiometers  
16  
 
Calibration Instructions  
4
4.1 Equipment Required  
1.  
• Precision mV source, with 0.001 mV resolution and 0.002mV  
accuracy or  
• Precision DVM with 0.002mV accuracy and adjustable mV  
source with 0.001mV resolution  
• OMEGA TRC III Ice Point Reference (or stable ice bath)  
Temperature Reference Probe (OMEGA P/N: TRP-(*))  
*Thermocouple Type: J, K, T, E  
2.  
• Or a Thermocouple Calibrator/Simulator  
17  
 
Calibration Instructions  
4
4.2 Set-up of Equipment  
To prepare the ice bath:  
a) Fill a glass beaker with crushed ice made from distilled water.  
b) Fill the beaker with enough distilled water so that ice just  
becomes slush, but not enough to float the ice.  
c) Insert the reference thermocouple.  
Figure 4-2 shows an alternate set-up. Here, a high precision  
thermocouple calibrator, such the OMEGA Model CL511, replaces  
the DVM, ice bath, voltage source, etc.  
18  
 
Calibration Instructions  
4
4.3 Calibration Procedures (Refer to Figure 4-1)  
Connect the calibration equipment according to Figure 4-1 or 4-2.  
The thermocouple wire (J, K, T, E) must be of the same  
calibration as the transmitter being calibrated. Make sure that the  
wiring polarities are correct. (Note that the RED thermocouple  
wire is NEGATIVE.)  
To check or adjust the calibration:  
1. Locate the Z (zero) and S (span) potentiometers.  
2. Select, from Table 4-1, the correct mV values for the Z (zero)  
and S (span) adjustments that correspond to the Model  
Number. For example, for Model TX91-J2, the Z input is -0.885  
mV, and the S input is 4.906 mV.  
19  
 
4
Calibration Instructions  
If a Thermocouple Calibrator/Simulator is used, such as the OMEGA  
Model CL511 Precision Calibrator, select the Temperature Input  
Z (zero) and S (span) values.  
3. Set the DC mV source to the selected Z (zero) mV value. Adjust the  
Z potentiometer to read 4.000 mA on the monitoring instrument.  
4. Set the DC mV source to the selected S (span) mV value. Adjust the  
S potentiometer to read 20.000 mA on the monitoring instrument.  
5. Repeat steps 3 and 4, as required, until the readings are exactly  
4.000 mA and 20.000 mA. This procedure is necessary since there is  
interaction between the two potentiometers.  
20  
 
Calibration Set-up  
4
21  
 
Figure 4-1. Calibration Set-Up  
Calibration Instructions  
4
SPAN  
TX91  
ZERO  
INPUT  
THERMOCOUPLE  
WIRE  
22  
Figure 4-2. Calibration Set-Up. (Alternate)  
 
4
Calibration Instructions  
Table 4-1. Calibration Values for the TX92  
Temperature  
Input Range  
Zero/Span  
mV INPUT  
REF 32°F  
Zero/Span  
mV INPUT  
REF 32°F  
Zero/Span  
Model  
TX92  
Model  
TX92  
0/1200°F  
0/1300°F  
0/1500°F  
0/1750°F  
0/1000°F  
0/1200°F  
0/1300°F  
0/1500°F  
0/1750°F  
0/1000°F  
-J2  
-J3  
-J4  
-J5  
-J6  
-T2  
-T3  
-T4  
--  
-0.855/14.906  
-0.885/17.947  
-0.885/14.108  
-0.885/20.406  
-0.885/29.515  
-0.674/13.967  
-0.674/16.647  
-0.674/12.572  
--0.674/12.572  
--0.674/12.572  
-K2  
-K3  
-K4  
-K5  
-K6  
-E2  
-E3  
-E4  
-E5  
-E6  
-0.692/13.819  
-0.692/16.092  
-0.692/10.560  
-0.692/15.295  
-0.692/22.251  
-1.026/15.869  
-1.026/19.708  
-1.026/17.942  
-1.026/26.858  
-1.026/40.056  
23  
--  
 
Troubleshooting Guide  
5
Malfunction or incorrect operation may be caused by:  
1. Reversed polarity:  
Check the wiring using Figure 3-5 as a guide. If the temperature  
of the thermocouple increases while the current magnitude  
decreases, the problem could caused by reversed polarity of the:  
a) thermocouple wiring  
b) power supply leads  
c) monitor instrument  
2. Loose or broken wires:  
Check each terminal connection for tightness. Move each wire  
back and forth and note any changes in operation.  
3. Too high a load resistance in the output current loop or too low  
a current rating on the power supply:  
24  
 
5
Troubleshooting Guide  
a) Measure the total resistance of each device (excluding the  
transmitter and power supply) in the 20 mA loop, including the  
resistance of the lead wires.  
b) Calculate the maximum allowable loop resistance using the  
formula:  
Loop Resistance (maximum) = Vsupply -11V  
0.020A  
For example, a 24V power supply would give a maximum loop  
resistance of: 13V/0.020A = 650 ohms.  
c) Make sure the power supply is rated for at least 28 mA times the  
number of TX91 transmitters being powered. For example, if the  
supply is powering 5 transmitters, the supply should be rated for  
at least 140 mA.  
25  
 
Accessories  
6
Model No.  
Description  
TX90-BR  
PSU-24B  
TX82A  
RT  
Mounting Bracket  
Unregulated Power Supply, 24 Volts  
Process Loop-Powered Indicator  
48” Mounting Track  
26  
 
Specifications  
7
General  
SIZE:  
1.75" dia. X 1.125" high (includes terminal strip)  
25%  
ZERO/SPAN ADJUSTMENT  
RANGE:  
POWER SUPPLY VOLTAGE  
OPERATING RANGE:  
+11VDC to +44VDC, 28 mA max required per  
transmitter  
ACCURACY:  
0.1% of full scale (includes effects of hysteresis,  
repeatability and linearity proportional to the T/C)  
AMBIENT TEMPERATURE:  
-13°F to 185°F (-25°C to 85°C)  
STORAGE TEMPERATURE  
RANGE:  
27  
-85°F to 193°F (-65°C to 89°C)  
 
Specifications  
7
THERMAL ZERO SHIFT:  
<0.01%/°F of span (span >5 mV)  
<0.02%/°F of span (2-5 mV span)  
<0.01%/°F of span  
THERMAL SPAN SHIFT:  
WEIGHT:  
1.5 oz (50g)  
Output  
CURRENT OUTPUT SPAN:  
CURRENT OUTPUT LIMITS:  
MAXIMUM LOOP  
RESISTANCE:  
4-20 mA DC  
3 to 28 mA, typical  
(Vsupply – 11V)/0.020A = ohms  
LOAD RESISTANCE  
EFFECT:  
POWER SUPPLY EFFECT:  
0.05% of span per 300 ohms change  
0.01% of output span per volt  
Input  
SENSOR:  
Thermocouple  
28  
IMPUT BREAK PROTECTION: Upscale  
 
IMPEDANCE:  
200K  
Appendix  
Intrinsically Safe Interconnection Diagram  
A
29  
 
WARRANTY/DISCLAIMER  
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a period of 13 months from  
®
date of purchase. The OMEGA WARRANTY adds an additional one (1) month grace period to the normal one (1) year product  
warranty to cover handling and shipping time. This ensures that OMEGA’s customers receive maximum coverage on each product.  
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service Department will issue an Authorized  
Return (AR) number immediately upon phone or written request. Upon examination by OMEGA, if the unit is found to be defective, it will  
be repaired or replaced at no charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser, including  
but not limited to mishandling, improper interfacing, operation outside of design limits, improper repair, or unauthorized modification. This  
WARRANTY is VOID if the unit shows evidence of having been tampered with or shows evidence of having been damaged as a result of  
excessive corrosion; or current, heat, moisture or vibration; improper specification; misapplication; or misuse or other operating conditions  
outside of OMEGA’s control. Components in which wear is not warranted, include but are not limited to contact points, fuses, and triacs.  
OMEGA is pleased to offer suggestions on the use of its various products. However, OMEGA neither assumes  
responsibility for any omissions or errors nor assumes liability for any damages that result from the use of its  
products in accordance with information provided by OMEGA, either verbal or written. OMEGA warrants only that the  
parts manufactured by the company will be as specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES  
OR REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESSED OR IMPLIED, EXCEPT THAT OF TITLE, AND ALL  
IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR  
PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF LIABILITY: The remedies of purchaser set forth herein are  
exclusive, and the total liability of OMEGA with respect to this order, whether based on contract, warranty,  
negligence, indemnification, strict liability or otherwise, shall not exceed the purchase price of the component upon  
which liability is based. In no event shall OMEGA be liable for consequential, incidental or special damages.  
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic Component” under 10 CFR 21  
(NRC), used in or with any nuclear installation or activity; or (2) in medical applications or used on humans. Should any Product(s) be  
used in or with any nuclear installation or activity, medical application, used on humans, or misused in any way, OMEGA assumes no  
responsibility as set forth in our basic WARRANTY/ DISCLAIMER language, and, additionally, purchaser will indemnify OMEGA and hold  
OMEGA harmless from any liability or damage whatsoever arising out of the use of the Product(s) in such a manner.  
 
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and Control?  
OMEGA…Of Course!  
Shop online at omega.com  
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