HVG-2020A Instruction Manual
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NOTICE: The load resistance be no less than 2 kΩ for voltage output to maintain accurate readings.
Optional to the standard voltage output is the 0-20 mA or 4-20 mA current output that is proportional to
pressure. The current loop output is useful for remote applications where pickup noise could substantially
affect the stability of the voltage output. The current loop signal replaces the voltage output on pin 5 of the D”
connector and is returned on pin 8.
NOTICE: The loop load must be less than 600 Ω. Failure to meet this condition will cause failure of the
loop transmitter. Wiring diagrams for power and 4-20mA signals are shown below.
NOTICE: The power requirements are greater when using 0-20mA and 4-20mA output signals.
NOTE: 0-20mA cannot indicate a negative zero offset.
2.3.4. Setpoints
The HVG-2020A has two open-drain setpoints available on the 9 pin D connector. The Hi setpoint will be active
when the pressure is above its set value and the Lo setpoint will be active when the pressure is below its set
value. There is a small amount of hysteresis built into the settings. Once a setpoint is activated, the pressure
must go 1 Torr beyond that value in the opposite direction to deactivate.
The set point values can be changed via the display (Setpoint View, Section 3.2) or serial communications (see
S20 and S21 commands). The setpoints will also show on the Bar Graph View as up and down arrows.
NOTICE: To utilize the open-drain setpoint pins, external pull-up resistors larger than 1 kΩ are
required. Do not apply more than 5 volts to the setpoint pins.
4 – 20 mA wiring diagram w/ unipolar supply