JH1200: Single Trip Alarm
JH1220: Dual Trip Alarm

  • Available for All Thermocouple Types
  • In-The-Terminal Cold Junction Compensation
  • Low-Drift Input Amplifier
  • Jumper-Selectable Upscale/Downscale Burnout
  • Switch-Selectable HI/LO Trip Function
  • Adjustable Deadband Standard
  • AC or DC Power Options




Models JH1200 and JH1220 Thermocouple Alarms monitor temperature as measured by a thermocouple and provide relay contact HI/LO trip outputs. Both are fixed-range devices, with input ranges preset per your order.

The alarm trip points are adjustable anywhere within the input range. Deadbands also are fully adjustable, from 0.25% to 100% of span. A slide switch, accessible through the top of the enclosure, selects HI or LO trip operation (on dual alarms, HI/HI, HI/LO or LO/LO). Red/green LEDs indicate alarm status. Model JH1200 provides one set of DPDT relay contacts; Model JH1220, two SPDT relays. Alarm contacts are rated at 5 amps, 230Vac or 30Vdc.

The cold junction sensor is encapsulated into the input terminals for maximum accuracy. A low-drift input amplifier maintains accurate setpoints with changing ambient temperatures. An internal jumper allows HI or LO trip indication upon thermocouple burnout.  AC and DC power options are available.


Model Number:  Select JH1200 single-trip alarm or JH1220 dual-trip alarm. Add suffix –AC for AC power or –DC for DC power.
Thermocouple Type:  Specify type J, K, T, E, R, S, B or N, or contact factory for others.
Input Range:  Specify any input range corresponding to 4mV or higher span. (4mV equals 100 deg. C for type K thermocouples.).
T/C Burnout Indication:  Specify upscale (high) or downscale (low) burnout indication. Will be set for upscale if not specified on your order.
Trip Point:  If you would like the trip points to be factory set, please specify the following for each trip point. Specify HI or LO trip, specify the setpoint and specify the amount of deadband required (or specify "minimum deadband").
Relay Action:  Standard is Failsafe - the relay is energized under normal conditions and deenergizes upon alarm or upon loss of power. Thus, loss of power is seen as an alarm condition. Or specify Option R (Reverse Acting) – relay is normally not energized and energizes (pulls in) upon alarm trip. Failsafe is provided if not specified.
Power:  Specify 115Vac, 230Vac, 12Vdc or 24Vdc.
Urethane Coating:  

Specify Option "U"


These alarms plug into any standard 11-pin circular ("octal") relay socket. JH Technology offers a socket suitable for DIN-rail or surface mounting (see the Accessories page).

The thermocouple connects to a small terminal block (which also contains cold junction compensation) on the side of the module. The remaining pin connections are:

Pin 1: Power (AC or, if DC power option, DC plus). 
Pin 2:
No connection. 
Pin 3:
Power (AC or, if DC power option, DC minus). 
Pin 4:
No connection. 
Pin 5:
No connection. 
Pin 6:
Setpoint 1 relay NO contact.* 
Pin 7:
Setpoint 1 relay moving contact.* 
Pin 8:
Setpoint 1 relay NC contact.* 
Pin 9:
Setpoint 2 relay NO contact.* 
Pin 10:
Setpoint 2 relay moving contact.* 
Pin 11:
Setpoint 2 relay NC contact.*

  • Notes: NO (normally open) and NC (normally closed) refer to the relay state when no power is applied. For Failsafe operation the NO contacts are closed under nonalarm conditions. The NC contacts close upon alarm and upon loss of power. The terms Setpoint 1 and Setpoint 2 refer to dual-trip alarms. For single-trip alarms, both sets of contacts respond to the one trip point.


Input Capabilities:  Any input span 4mV or higher. Offset ranges are allowed.
Input Thermocouple Type:  Any standard thermocouple type (J, K, T, E, R, S, B, N). Others possible – contact factory.
Thermocouple Burnout Indication:  Jumper-selectable upscale (offscale high) or downscale (offscale low). Factory set for upscale unless otherwise specified.
Relay Contacts:  Single Alarm, one DPDT relay. Dual Alarm, two SPDT relays. Contacts rated 5 Amps resistive, 115/230Vac or 30Vdc. 1/8 HP max inductive load at 115/230Vac. Refer to instructions for contact protection when switching inductive loads.
Setpoint Adjustment:  0% to 100% of range.
Deadband Adjustment:  0.25% to 100% of range.
Response Time:  under 100 milliseconds.
Isolation:  Input is isolated from power and from relay contacts. 1,500Vac rms (2,100V peak) breakdown.
Guaranteed Operating Temperature:  -10 to +60 deg. C (14 to 140 deg. F).
Temperature Stability:  +/-(0.02% of span plus 1.3 microvolts) per deg. C, or better.
Power Requirements:  AC, 115 or 230Vrms, 50/60 Hz., 2.5V-A. DC, 12 or 24Vdc, 2.5W.