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E40MH1
GENERAL DESCRIPTION:
Electronic Designs Incorporated’s (EDI) E40MH1 solid state timers are capable of switching
twenty (20) independent outputs. Each of the outputs has a switching capacity of 1 Amp at
110 VAC. By relocating the program wire from Position #40 (on the Timer) to the number of
positions desired, the timer will pulse only from Position #1 through the programmed number.
The LED display indicates the next output to fire.
The E40MH1 is equipped with dual functions, allowing the customer a choice of operating
modes. The timer can operate in response to a 4-20 ma signal from the Differential Pressure
Transmitter or it can operate as a Hold-Off timer with the off-time set on the timer.
Additionally it can operate in Continuous Cycle Mode. We recommend use of the EDI
Differential Pressure Transmitter in conjunction with this timer for optimum operation.
SUMMARY OF OPERATING MODES:
1. 4-20 ma Cycle Mode
The input is a 4-20 ma linear signal, corresponding to a differential pressure of 0-10
inches of water. The timer will continuously monitor the 4-20 ma input signal and
automatically adjust the OFF time for the output pulse. In this mode, the OFF-ADJ
potentiometer is inactive and does not control the duration of OFF time between each
output firing. (Switch SW1 must be set in the OFF position ↓)
During operation, as the differential pressure starts to rise, the timer will decrease the
OFF time in response. If the differential pressure should rise greater than the set point
level, the timer will pulse at the fastest OFF time rate of 3 seconds. As the differential
pressure decreases to and below the set point, the OFF time will proportionally
increase to a level which will maintain the desired set point differential pressure.
2. Hold-OFF Mode
In the Hold-OFF mode, the OFF time is preset by means of the OFF-ADJ
potentiometer on the timer (Time duration is set by operator). This provides a fixed
OFF time. The input signal to the timer is 110VAC, which is applied to the Hold-OFF
circuit of the timer. When 110VAC is applied to these terminals, the output pulse
becomes inactive until the 110VAC is removed. The timer resumes it’s cycle on the
next output to be fired. (SW1 must be in the ON position ↑)
This input enables the timer to start and stop the pulse cycle via auxiliary switch, such
as a Differential Pressure Transmitter, Computer Contacts or Pressure Switch.
3. Continuous Cycle Mode
Lastly, the timer can function as a continuous cycle timer, with no Hold-Off signal
applied. This is achieved by placing SWITCH SW1 in the ON position ↑.
