Teledyne 3020M - Explosion proof paramagnetic oxygen analyzer - Manual (Page 30)

3 Installation Model 3020M
3-8 Teledyne Analytical Instruments
NOTE: Power may be present on this contacts even when power to
analyzer has been removed since this contacts are wired by
the customer.
3.3.5 Digital Remote Cal Inputs
Remote Zero and Span Inputs: The REMOTE SPAN and RE-
MOTE ZERO inputs are on the DIGITAL INPUT terminal block. They
accept 0 V (OFF) or 24 V dc (ON) for remote control of calibration. (See
Remote Calibration Protocol below.)
ZERO: Floating input. 5 to 24 V input across the + and – terminals
puts the analyzer into the
Zero mode. Either side may be
grounded at the source of the signal. 0 to 1 volt across the
terminals allows
Zero mode to terminate when done. A
synchronous signal must open and close the external zero
valve appropriately. See 3.3.9 Remote Sensor and Solenoid
Valves. (With the –C option, the internal valves automatically
operate synchronously.)
SPAN: Floating input. 5 to 24 V input across the + and – terminals
puts the analyzer into the Span mode. Either side may be
grounded at the source of the signal. 0 to 1 volt across the
terminals allows
Span mode to terminate when done. A
synchronous signal must open and close the external span
valve appropriately. See 3.3.9 Remote Sensor and Solenoid
Valves. (With the –C option, the internal valves automatically
operate synchronously.)
Cal Contact: This relay contact is closed while analyzer is spanning
and/or zeroing. (See Remote Calibration Protocol below.)
Remote Calibration Protocol: To properly time the Digital Remote
Cal Inputs to the Model 3020M Analyzer, the customer's controller must
monitor the CAL CONTACT relay.
When the contact is OPEN, the analyzer is analyzing, the Remote Cal
Inputs are being polled, and a zero or span command can be sent.
When the contact is CLOSED, the analyzer is already calibrating. It
will ignore your request to calibrate, and it will not remember that request.
Once a zero or span command is sent, and acknowledged (contact
closes), release it. If the command is continued until after the zero or span is
complete, the calibration will repeat and the Cal Relay Contact (CRC) will
close again.
For example: