TX253-R--S-Type-TC-Tx

Supported Applications

The Omega TX250 Series comprises non-isolated, head-mount signal conditioners designed to convert thermocouple thermoelectric voltage or 3-wire Pt100 RTD signals into a standardized process current. The series includes models for Types J, K, T, E, R, and S thermocouples as well as 3-wire 100 Ω Platinum (Pt) RTDs. These transmitters are housed in metal enclosures that fit into NB1 connection heads.

Key operational characteristics include:

• Conversion of sensor input to a 4 to 20 mA output signal
• High RFI immunity for industrial environments
• Non-isolated design intended for use with ungrounded probes

Note: The TX250 series is marked as DISCONTINUED in the source documentation.

Operating Conditions & Performance

The TX253 model within this series supports R and S type thermocouple inputs with a measurement span of 0 to 1750°C (32 to 3180°F). The minimum required span for these models is 600°C (1080°F), with a zero offset range from 0 to 750°C. Accuracy specifications are listed as better than 0.1% of span or better than 0.08% of span depending on configuration.

Performance parameters include:

• Ambient operating temperature: -20 to 70°C (-4 to 158°F)
• Humidity rating: 5 to 95% RH, non-condensed
• Power supply requirement: 10 to 36 Vdc (24 Vdc recommended), with excitation current less than 1 mA
• Output signal limit: 4 to 20 mA, limited to 28 mA
• Load resistance calculation: Rmax (Ω) = (Vsupply - 10)/0.02

The transmitters are linear to the mV input from the thermocouple rather than being linearized directly to temperature.

Voltage and Current Specifications

• Excitation voltage: <1 mA
• Power supply range: 10 to 36 Vdc
• Output current limit: 28 mA limited

Configuration Options

The TX250 series offers configurable options for input types, scaling, and power supply integration. While the standard factory settings are fixed (e.g., TX253 Type R at 0 to 1700°C), custom ranges can be specified via a separate ordering process.

• Input Types: Models cover J, K, T, E thermocouples; R and S type high-temperature thermocouples (TX253); and 3-wire 100 Ω Pt RTDs (TX254).
• Housing & Mounting: Diecast zinc alloy enclosure with dimensions of 33 H x 44 mm diameter (1.3 x 1.7") including the terminal block; fits NB1 protection heads.
• Electrical Connection: 2-wire, screw terminal block featuring 5 positions.
• Scaling Options: Custom ranges are available by ordering TX-SCALED and specifying input type, low end of range, and high end of range (C or F).

Power Supply Accessories

The series supports several power supply options for system integration:

• PSR-24S: Regulated 24 Vdc, 400 mA with screw terminal.
• PSR-24L: Regulated 24 Vdc, 400 mA, UL listed with stripped leads.
• PSR-24L-230: Regulated 24 Vdc, 400 mA with stripped leads and 230 Vac input (CE).
• PSU-93: Unregulated power supply, 16 to 23 Vdc, 300 mA max.

Key Product Differences

The TX250 series is differentiated by model number based on the supported sensor input type and measurement range:

• TX251: Transmitter for J, K, T Type thermocouples.
• TX252: Transmitter for E Type thermocouples.
• TX253: Transmitter specifically for R and S Type thermocouples (0 to 1750°C / 32 to 3180°F).
• TX254: Transmitter for 3-wire 100 Ω Platinum RTDs (-50 to 750°C / -58 to 1380°F).

Calibration is set via DIP switches and trimmers. Field scaling requires calibration equipment, as the units are not linearized to temperature by default but output proportional to mV.