ETTR: Programmable Temperature Relay


  • Inexpensive, microprocessor based design
  • User programmable using GUI software
  • Relay output, SPDT 1A contact
  • Programmable hysteresis and minimum cycle timing
  • Programmable LOCKOUT to prevent cycling after a certain temperature has been reached.
  • Stand alone operation with remote monitoring option
  • May be programmed for custom thermistor curves (10k)
  • Set includes 10 k thermistor, mounting track and programming software


The ETTR may be used as a simple temperature controller, providing on/off relay output for fans, heaters, shut off valves and safety systems. Because of its software adjustable parameters, the product is highly customizable - an ideal solution for many OEM temperature control applications.

Product Description

The ETTR is a programmable temperature relay with the ability to act as an ON/OFF temperature controller. The device is capable of fully stand alone operation, but may be monitored and programmed with the custom software and a serial RS232 interface.

The unit may be programmed to work in various modes:

  1. Range (ON/OFF)- will turn the relay on/off between two defined temperature values
  2. Setpoint (Heating/Cooling) - will turn the relay (off/on) above a set value, and (on/off) above a second set value
  3. Manual - Allows manual (via PC) control of the output relay

The span between the temperatures in Setpoint mode may be used to adjust the hysteresis of the device. An adjustable short cycle timer may be configured to prevent rapid cycling of the relay.

A lockout feature is implemented to maintain the output relay status after it switches. This may be used in an alarm condition to alert the operator that an over/under temperature situation occurred. Power cycling the device resets it.

The GUI allows monitoring of the temperature, and provides information on the status of the device (including communication timeouts and Thermistor wiring errors). The GUI also allows logging of temperature data to an ASCII text file in a semi-colon delimited format which may later be imported to a spreadsheet application such as Excel.

The ETTR is compatible with ANY 10 k ohm thermistor. Software version 2.2 and up now supports inputting of custom R/T curve for use with other thermistors. Up to 100 R/T points may be entered, and the software will use linear interpolation between points to calculate accurate temperatures!


Power12 to 24 VDC (100mA minimum) or 18 to 24 VAC
InputSingle NTC 10 k thermistor in brass tubing (provided)

Customer provided 10 k thermistor may be used with new software version by inputting the R/T curve for the given thermistor.

(Min Resistance = ~650 ohms)
(Max Resistance = ~130k ohms)

OutputForm C output relay (rated 1A @ 24 VAC/VDC) (low voltage)
IndicationStatus - Green LED
solid = Power ON
flashing = Thermistor wiring fault
Temperature Range-25°C to 100°C (-13°F to 212°F)
Computer InterfaceSerial communications via RS232 port, Windows« based software provided. Communications protocol available upon request. Please contact Elkor Technologies Inc. for more information.
Dimensions1" x 2.25" (26 x 57 mm), board mounts in TR-1 plastic snap-track (provided)

Ordering Information

ETTR fully describes this product



ETTR Software
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