2-RELAY PROCESS 4-20 mA LOOP INDICATOR / MONITOR / WINDOW COMPARATOR OVER / UNDER PROTECTION with 24V power supply ( to power external loop)


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The input signal is converted and displayed as real-world values with up to 3 decimal places.
Maximum & Minimum values are logged for 24 hours (updated every 60 min).
By default the re-transmittion parameters are set so that the output follows the input.
By setting the Span to a negative value, the device can be used as an inverter, generating a decreasing output signal as the input increases.
Other features include user programmable signal damping & all settings may be locked & code protected to avoid changes from being made by unauthorised personnel 


The relays remain energised while the input signal is between the upper and lower set points.
Once de-energised, the signal must change in the opposite direction by the hysteresis amount before the relay will re-energise.
Shorting the latch pins, forces the relay to remain de-energised after a fault condition (until the short is removed).
The relay action may be swapped to energise when the setpoint is reached.
The signal recieved is converted and displayed as ‘real world’ values. (eg 0-100 °C ,not 4 -20mA).
By setting the span to a negative value, the display will indicate lower values as the input rises.



  • monitor for "OVER"/"UNDER" value conditions
  • independantly reverse relay(s) action (energise or de energise when fault occurs)
  • adjustable hysteresis (differential)
  • negative span values allows display to reduce in value as input increases (eg 100%=4mA, 0% = 20mA)
  • adjustable resolution, by adjusting decimal point
  • seperate upper and lower set points allows the device to be set for OVER, UNDER or WINDOW COMPARATOR monitoring
  • adjustable "START UP" delay, allows input to stabalize at power up before monitoring starts
  • adjustable "TRIP" delay (reaction delay) allows fault conditions for short period of time
  • activate the "LATCH" facility independantly for each relay (use one relay to control, and another to latch alarm conditions)
  • adjustable calibration facility allows the user to improve overall system accuracy (compensate for transducer inaccuracy)
  • keypad lock with 4-digit code
  • re transmit the signal (or any part thereof) as 4-20mA, set re transmit offset and span to any value within the display scale.


DISPLAY OFFSET:                    -999 to 9999

DISPLAY SPAN:                       -1999 to 9999

DISPLAY RESOLUTION:           0.01 to 1.000 (adjustable)

INPUT OFFSET:                        0 to 20.6mA

INPUT SPAN:                           0 to 20.6mA

24V DC supply current limit (-P devices only): 23mA


RESPONSE TIME:                     <1-4sec

RELAY 1 and RELAY 2: UPPER/LOWER Limits:        set independantly : any value within scale

RELAY 1 and RELAY 2: HYSTERESIS:                       set independantly : any value within scale

RELAY 1 and RELAY 2: START UP/TRIPP DELAY:     set independantly : 0-99 sec

RELAY 1 and RELAY 2 :LATCH enable:                      set independantly : ON/OFF

RELAY 1 and RELAY 2:relay function:                      set independantly : energise/de energise



Display offset:                -999 to 9999

Display span:                  -1999 to 9999

Display resolution:          0.01 to 1.000  (adjustable)

Input offset:                    0 to 20.3V

Input span:                      0 to 20.3V (offset + span maximum = 20.3V)

Measurement resolution: 20 uA

Accuracy                          ±0.3% @ 25°C (% of full scale)

Input voltage:                 ±15% of rated input