Omega TX94A User manual

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TX94A
Ultra-Miniature
Temperature Transmitters
TM
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User’s Guide

The information contained in this document is believed to be correct, but OMEGA accepts no liability for any errors it contains, and reserves
the right to alter specifications without notice.
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TABLE OF CONTENTS
Section 1 Getting Started
1.1 Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.2 Safety and EMC Considerations . . . . . . . . . . . . . . . . . . .1
1.3 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1.4 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1.5 Models Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Section 2 Installation
2.1 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.2 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Section 3 Calibration Instructions
3.1 Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3.2 Set-up of Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3.3 Calibration Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . .7
Section 4 Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Section 5 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

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FIGURES & TABLES
Figure 1-1 RTD Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Figure 2-1 Assembly inside a Protection Head . . . . . . . . . . . . . . . . . . . .4
Figure 2-2 Wiring Diagram for RTD Transmitter . . . . . . . . . . . . . . . . . . .5
Figure 3-1 Transmitter Calibration Set-Up . . . . . . . . . . . . . . . . . . . . . . . .7
Figure 5-1 Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Table 1-1 Range Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Table 1-2 Model Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Table 3-1 Calibration Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

1.1 Unpacking
Remove the packing list and verify that you have received all equipment. If
you have any questions, contact the nearest Customer Service
Department, as listed on the cover of this manual.
Upon receipt of shipment, inspect the container and equipment for any
signs of damage. Note any evidence of rough handling in transit.
Immediately report any damage to the shipping 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 materials and carton in the event
reshipment is necessary.
1.2 Safety and EMC Considerations
This instrument is a Class III device (8 to 35 Vdc).
Always use a power supply, which complies with EN 60950 safety
standard.
•Do not expose the transmitter to rain or condensing moisture.
•Do not operate the transmitter in flammable or explosive atmosphere.
•As with any electronic instrument, you may encounter high voltage
exposure when installing, calibrating or removing parts of the
transmitter.
EMC Considerations
•Whenever EMC is an issue, always use shielded cables.
•Never run signal and power wires in the same conduit.
•Use signal wire connections with twisted-pair cables.
•Install Ferrite Bead(s) on signal wires close to the instrument if EMC
problems persist.
Failure to follow all instructions and warnings may result in injury!
1.3 General Description
The Two-Wire RTD Transmitter will produce a standard 4-20mA output
signal proportional to that produced by its RTD input temperature sensor.
Transmission of the proportional current output may be accomplished by
using inexpensive copper wire. The RTD transmitter accepts two-wire or
three-wire ohm platinum RTD sensors (PT100,alpha = 0.00385).
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1.3 General Description
The transmitter is normally powered by an unregulated power supply as
shown in Figure 1-1. The proportionally-transmitted signal begins at 4mA,
at the low end of its temperature range, and increases to 20mA, at the
high end of its temperature range. (There are various temperature ranges
available for the transmitter. To order, refer to Section 1.5 for correct
Model Numbers and Range Codes.)
Figure 1-1 RTD Transmitter
The transmitter works with 2 or 3-wire RTDs and provides an output
current of 4-20mA proportional to the RTD Sensor.
When the transmitter is mounted inside a protection head, (see Figure 2-1),
two copper wires now carry the temperature signal and dc voltage to
operate the transmitter, thereby reducing possible noise pick-up errors.
The transmitter does NOT provide isolation between its input and the
4-20 mA output. Note, however, that the RTD element is electrically
insulated.
1.4 Features
• +/-0.1% full-scale accuracy (with respect to the RTD input
resistance)
• 4-20 mA output
• Upscale break protection
• Low Cost
FIELD CONTROL ROOM

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1.5 Models Available
Table 1-1 Range Code
INPUT TYPES
RANGE RTD
-40 to 120 F (-40 to 49 C) 1
0 to 200 F (-18 to 93 C) 2
0 to 300 F (-18 to 149 C) 3
0 to 500 F (-18 to 260 C) 4
0 to 750 F (-18 to 399 C) 5
0 to 1000 F (-18 to 538 C) 6
Table 1-2 Model Numbers
Model Number Description
TX94A-(*) RTD Transmitter (100 ohm, Pt,
alpha=0.00385)
*Insert range code from Table 1-1

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2.1 Mounting
The transmitter may be:
1. surface mounted
2. mounted inside a protection head (shown in Figure 2-1)
Figure 2-1 Assembly of the Transmitter
inside an PR-14 Protection Head
SECTION A-A
POWER LINES
RTD WIRES

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2.2 Wiring
Refer to Figure 2-2
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 RTD element to the (+IN) and (-IN) input terminals.
Figure 2-2 Wiring Diagram for RTD Transmitter
3-WIRE
RTD
RED
BLACK
RED
BLACK
JUMPER
WIRE BLACK
2-WIRE
RTD

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3.1 Equipment Required
• Precision Decade Resistance Box, with 0.01 ohm resolution and
±0.02 ohm accuracy
or
• Precision RTD Simulator, such as OMEGA CL511 Precision Calibrator
• Precision DMM capable of measuring mA, within 0.001 mA resolution
and ±0.002 mA accuracy
3.2 Calibration Procedures
Connect the calibration equipment according to Figure 3-1. Standard
copper test leads are used with RTD instrumentation.
To check or adjust the calibration:
1. Locate the Z (zero) and S (span) potentiometers.
2. Select, from Table 3-1, the correct ohmic values for the Z (zero) and
S (span) adjustments that correspond to the model number.
For example, for Model TX94A-2, the Z value is 92.95 ohms, and the
S value is 135.84 ohms.
If a Thermocouple/RTD Simulator is used, such as the Model CL511
Precision Calibrator, select the Temperature Input Z (zero) and
S (span) values.
3. Set the Decade Box to the selected Z (zero) ohmic value. Adjust the
Z potentiometer to read 4.000 mA on the monitoring instrument.
4. Set the Decade Box to the selected S (span) ohmic 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.