TX93A-TX94A

Supported Applications

The Omega TX93A and TX94A series are ultra-miniature temperature transmitters designed to convert millivolt inputs from thermocouples or resistance from RTDs into a stable 4 to 20 mA DC output. These units eliminate long runs of costly field wiring by transmitting the signal via a twisted pair of copper wires, which reduces noise pickup, voltage drops, and multiple cold junction errors.

Designed for compact installations, these transmitters fit inside thermowell protection heads such as the Omega NB2 aluminum head or PR14 miniature aluminum head. The series supports applications requiring:

• Type J, K, T, and E thermocouple inputs (TX93A)
• 3-wire 100 Ω Platinum RTD inputs with alpha = 0.00385 (TX94A)

Operating Conditions & Performance

The TX93A/TX94A series operates within an ambient temperature range of -25 to 85°C (-13 to 185°F) and can be stored between -65 to 125°C (-85 to 257°F). The transmitters provide a response time of 3 dB @ 3Hz. Accuracy is specified as ±0.1% FS, which includes the effects of linearity, hysteresis, and repeatability.

Power requirements are 8 to 35 Vdc (24 Vdc recommended), with a load resistance capability defined by Vs - 8V / 0.020 A. The output signal is adjustable ±25% for zero and span calibration. Note that thermocouple models produce an output proportional to the mV output of the thermocouple; they are not linearized to temperature.

Configuration Options

The series offers configurable options regarding sensor type, measurement range, environmental protection, and assembly style. The base units feature color-coded enclosures (silver, black, yellow, green) with overall dimensions of 23.6 H x 35.6 mm D (0.93 x 1.40"), including the terminal strip.

Measurement Ranges

The series supports six standard temperature ranges:

• -40 to 49 °C (-40 to 120 °F)
• -18 to 93 °C (0 to 200 °F)
• -18 to 149 °C (0 to 300 °F)
• -18 to 260 °C (0 to 500 °F)
• -18 to 399 °C (0 to 750 °F)
• -18 to 538 °C (0 to 1000 °F)

Options and Assemblies

Beyond the standalone transmitter, the series includes specific configurations:

• Fully epoxy-potted electronics (-P option): Available for extreme environments; increases unit weight to 25 g (0.8 oz) from the standard 15 g (0.53 oz).
• NB2TX93A assembly: TX93A mounted into an NB2 aluminum protection head with a 12" ungrounded probe, ¼" diameter, and 304 SS sheath.
• PRTX94A assembly: TX94A mounted into a PR14 miniature aluminum protection head with a 12" stem length and ¼" probe diameter.
• Special factory scaling (-FS): Available for custom range requirements.

Electrical Connections

The units utilize a terminal strip connection (2 PLCS for #6-32 screw) and require only a twisted pair of copper wires for loop connections. These are non-isolated units intended for use with ungrounded probes.

Key Product Differences

Differences within the series are defined by sensor technology, environmental protection level, and mechanical assembly:

• TX93A vs. TX94A: The TX93A is a thermocouple transmitter supporting types J, K, T, or E. The TX94A is an RTD transmitter for 100 Ω Platinum sensors (alpha = 0.00385).
• -P Suffix: Indicates fully epoxy-potted electronics; standard models do not include this potting.
• NB2TX93A and PRTX94A Prefixes: Denote complete assemblies where the transmitter is pre-mounted into a specific aluminum protection head with an integrated probe, as opposed to the standalone transmitter unit which requires separate mounting.