Chapter Two: Installation Electrical Information
19
Set Point Input (Pin 8)
The set point input signal can be a 0 to 10 Volt (factory setting) or 0 to 5 Volt signal. The range
of the set point input signal must match the range of the pressure output signal. The 649
controller is initially configured for a 0 to 10 Volt pressure output signal. Therefore, the set point
input signal must be 0 to 10 Volts, where 10 Volts represents 100% of full scale. To change the
range of the pressure output signal to 0 to 5 Volts, you must reposition jumpers on the Transducer
board. Refer to page 39, for instructions on changing the pressure output range.
Note
The 649 controller must have sufficient pressure on its inlet side to
achieve the set point.
Flow Output Signal (Pin 9)
The flow output signal is available on pin 9. You can introduce this signal into another system to
monitor the flow rate. The flow output signal is 0 to 5 Volts, which is standard for most thermal
mass flow meters.
Optional Input (Pin 10)
Use pin 10 to introduce another signal, such as a zero corrected pressure signal, into the control
circuitry of the 649 controller. When a signal equal to or greater than 0.25V is introduced on pin
10, it overrides the Pressure Output signal (pin 2) until the signal on pin 10 drops below -0.8V.
Note
To assure the Optional Input is disabled, pin 10 should be left floating or
the voltage on pin 10 should be held below –1V (but no lower than -14V).
The Trip Point Outputs (Pins 13 and 14)
The 649 controller offers two alarm trip points: Trip Point A and Trip Point B. Each trip point
has an LED and adjustment pot on the top cover. The trip points are open collector transistors.
The trip points can be set from 1 to 100% of full scale by adjusting the appropriate trip point pot
located on the top of the unit. The trip point setting is a 0 to 5 VDC signal available inside of the
unit.
Use the appropriate trip point output signal to control a relay or another piece of equipment, such
as a valve, or as a digital input to a computer. The trip point signal is pulled to ground when the
trip point is on. The voltage value of the pin is 5 Volts when the respective trip point is off.
Refer to Trip Points, page 30, for a complete description of the trip points.
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