Alicat P Series Pressure Gauge - Manual (Page 26)

26
LOOP
VAR
OFF
AUTO PID MAIN
SETPT
SOURCE
CONTROL SETUP (conti nued)
Tareing (or zeroing) a gauge pressure or
diff erenti al pressure controller provides it
with a reference point for zero pressure.
OFF AUTO / ON AUTO—this feature allows
you to tare the controller.
The controller must be left in the default
OFF AUTO mode except when actually
tareing the controller as explained below.
It is, however, very important to perform
this adjustment only when you are
certain that the process ports are open to
atmosphere and that there is No Flow!
For liquid pressure devices, all liquid must be drained from the system.
To correctly tare a gauge pressure or diff erenti al pressure controller:
1. Be sure the unit is in the OFF AUTO default setti ng.
2. Disconnect all plumbing and make sure there is No Flow.
3. Push the butt on below OFF AUTO once so that the display reads ON AUTO.
4. Enter a Set-Point of ZERO. A zero set-point results in the closing of the valve
and a known “no fl ow” conditi on.
5. Wait at least 30 seconds.
6. Push the butt on below ON AUTO once so that the display reads OFF AUTO.
7. Reconnect the plumbing.
If the unit reads signifi cantly diff erent than zero, when removed from
the line and open, it is a good indicati on that it was given a false zero.
If your pressure controller was ordered with the opti onal “Tare-P”, you
may tare it following the instructi ons for tareing a pressure gauge on
page 16
Do Not Att empt To Tare Absolute Pressure (psia) Instruments!