Teledyne 4040 - Methane / Nonmethane analyzer - Manual (Page 32)

Installation Series 4040
32 Teledyne Analytical Instruments
3.3.3.6 D IGITAL R EMOTE C AL I NPUTS
The digital remote calibration input accepts 0 V (off) or 24 V dc (on)
for remote control of calibration. (See Remote Calibration Protocol
below.) See Table 3-5 for pin connections.
Span: Floating input. A 5–24 V input across the + and – pins puts the
analyzer into the Span mode. Either side may be grounded at the
source of the signal. A 0–1 volt across the terminals allows Span
mode to terminate when done. A synchronous signal must open
and close external span valve appropriately.
Cal Contact: This relay contact is closed while analyzer is spanning.
(See Remote Calibration Protocol below.)
Table 3-5: Remote Calibration Connections
Pin Function
10 + Remote Span
12 – Remote Span
40 Cal Contact
41 Cal Contact
Remote Calibration Protocol: To properly time the Digital Remote Cal
Inputs to the Model 4020 Analyzer, the customer's controller must
monitor the Cal Relay Contact.
When the contact is OPEN, the analyzer is analyzing, the
Remote Cal Inputs are being polled, and a 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 span command is sent, and acknowledged (contact closes),
release it. If the command is continued until after the span is complete,
the calibration will repeat and the Cal Relay Contact (CRC) will close
again.
For example:
Test the CRC. When the CRC is open, send a span command until the
CRC closes (The CRC will quickly close.)
When the CRC closes, remove the span command.
When CRC opens again, the span calibration is done, and the sample
is being analyzed.