Model 657C-1 Relative Humidity/Temperature Transmitter

Dual Channel Design for Simultaneous 4-20 mA Output Signals – Conduit Housing

The Series 657 Transmitters provide two 4 to 20 mA channels to produce separate output signals for both relative humidity and temperature. These devices deliver ±2% accuracy for humidity and ±1°F for temperature measurements. Stainless steel probe can be easily mounted to most ductwork using either of the two optional kits below.

NIST CALIBRATION available in Product Configurator.

Product Applications

  • Cleanroom monitoring
  • HVAC/building control monitoring

Models & Ordering

Shipping Information

All shipping times are dependent on product availability at time of shipment.

Although we make every effort to ensure a continuous supply of our products, occasional circumstances may force us to temporarily run out of a product, or have shipping delays. Should this occur, customers will be notified soon after placement of any orders for such products and, if applicable, items will be put on backorder. For orders requiring expedited shipment, our customer service team can be contacted to confirm product availability

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Model Description Usually Ships* Price Order
Ships: Next Day
Price: $364.00
Relative humidity/temperature transmitter. Next Day* $364.00 Order

Can't find what you need? Build Your Custom Part. Use our Product Configurator


Humidity & temperature detection in air.
Relative Humidity: 0-100%; Temperature: 32 to 212°F (0 to 100°C).
Relative Humidity: ±2% (10-90% RH), ±3% (0-10% and 90-100% RH); Temperature: ±1°F (0.5°C).
Temperature Limits:
32 to 140°F (0 to 60°C).
Pressure Limits:
1 psi (.07 bar).
Compensated Temperature Range:
32 to 140°F (0 to 60°C).
Power Requirements:
10-35 VDC.
Output Signal:
2 channels each 4-20 mA. Loop powered on the RH channel.
Electrical Connections:
4 screw type terminal.
Mounting Orientation:
Mount in any position.
5/16" x 9-1/10" (0.8 x 23.1 cm) stainless steel.
10 oz (284 g).


  • Polymer film humidity and thin film RTD temperature sensors offer highly reliable and stable measurements.
  • Rugged die-cast aluminum housing is great for industrial applications


Model Number Description Usually Ships* Price Order
Split flange. A-158 Split flange. Next Day $16.50 Order
Mounting gland with 1/2 A-159 Mounting gland with 1/2" male NPT. Next Day $32.75 Order

Model Chart

EXAMPLE 657C-1 AT Model 657C-1-AT Relative Humidity/Temperature Transmitter, with aluminum tag.
MODEL 657C-1   Relative Humidity/Temperature Transmitter
Aluminum Tag
NIST Certificate of Calibration
Stainless Steel Tag

Product Literature


Catalog Pages



I'm looking for a dual temp. and humidity gauge for an 8" duct. I'm wanting to remote read the temp and humidity on the incoming and outgoing air to an ERV unit. The RHP-3M11-LCD was recommended to me, however, it is a direct read. What would be the correct instrument to remote read the temperature and humidity from a distance of 8 feet. The 8" duct is in the attic and I want to read the result in the down-stair hall. I don't want to record nor program the unit, just read the performance.
The sensor recommended would be the best option we have for sensing temperature and relative humidity for your application. We do not have any options with a remote display that could stretch as far as you are asking, nor are there any on the market to my knowledge. In every case, you would need to utilize a process output, in this case 4-20 mA, to transmit the readings to a remote display(s) which would accept the process signal(s). If you are just looking for a remote readout to go with the RHP sensor with no control functionality, then you could look at one of our panel meters, possibly the SPPM, DPMA, DPMW, or DPMP & DPML series panel meters. For assistance selecting an appropriate panel meter, please contact our technical support group at 219-879-8000.

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