Instrutech VGC301 User Manual page 15

Instruction Manual
SET ATM
1. To set the atmospheric pressure reading (also known as the "span" adjustment), flow nitrogen gas or air
into your closed vacuum chamber to allow the pressure to rise to a known value above 400 Torr.
Alternatively, if your local uncorrected barometric pressure (air) is known, simply vent your vacuum
system chamber to expose the gauge to the local atmospheric pressure.
2. Go to the SET ATM screen. When the desired pressure is stable, adjust the displayed pressure reading
on the VGC301 to the known value using the INCR (increase) or DECR (decrease) keys. Press the
SAVE/EXIT key to save the new atmospheric (span) pressure value.
It is good practice to perform the sequence of checking and adjusting span (ATM) then zero (VAC) and
then, finally re-checking the span setting to ensure that the circuitry is properly balanced for use in
measuring pressure throughout the intended measurement range.
SP1 ON and SP2 ON [Factory default = 100 mTORR]
These setpoints correspond to the pressures at which the relays will turn on (energize). The relays will turn on
when the pressure is below the programmed pressure value. If you are unable to increase the values of SP1 ON
or SP2 ON , you must first go to SP1 OFF or SP2 OFF and increase those values to a number higher than the
values of SP1 ON or SP2 ON you are trying to set.
SET SP1 OFF and SET SP2 OFF [Factory default = 200 mTORR]
These setpoints correspond to the pressures at which the relays will turn of (de-energize). The relays will turn
off when the pressure is above the programmed pressure value. If you are unable to decrease the values of SP1
OFF or SP2 OFF, you must first go to SP1 ON or SP2 ON and decrease those values to a number lower than the
values of SP1 OFF or SP2 OFF you are trying to set.
RS485 ADDR [Factory default = 1]
This is the lower nibble of the one byte RS485 device address. Assuming the address offset (ADDR OFFSET) is
equal to 0, setting the ADDR to a 5 will make the address be 0x05 in hexadecimal. A 15 will set the ADDR to
0x0F in hexadecimal. Note that the address (ADDR) must be used even when sending RS232 commands
RS485 OFFSET [Factory default = 0]
This is the upper nibble of the one byte RS485 address. Assuming the address (ADDR) is 0, setting the address
offset (ADDR OFFSET) to a 5 will make the address be 0x50 hexadecimal. Setting the address offset to 15 will
make the device address be 0xF0 hexadecimal.
┌ -------------------------------------ONE BYTE-----------------------------------┐
ADDRESS
DECIMAL
1
5
15
16
InstruTech, Inc.
┌ -----------------------------BINARY ADDRESS-----------------------------┐
ADDR OFFSET
┌Upper nibble┐
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 1
(BINARY)
ADDR
┌Lower nibble┐
0 0 0 1
0 1 0 1
1 1 1 1
0 0 0 0
VGC301 Controller
ADDRESS
HEXADECIMAL
01
05
0F
F0
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