Teledyne 4020 – Hydrocarbon analyzer (special version for automatic background gas switching) - Manual (Page 40)

Installation Model 4020
Teledyne Analytical Instruments 22
synchronized with the switching of background gases. This signal
should be 24VDC to the Remote Zero Contacts as shown in Table 3-5.
This informs the 4020 Analyzer that it should use the calibration
parameters for a particular background gas. The analyzer will open or
close the background gas relay (AL-2) contact depending on the
currently selected background gas (either by manual selection via the
Background Gas display menu or by the remote zero contact).
Digital Remote Span Calibration
Since the input formerly assigned to digital remote zero is used for
background gas selection, there is no digital remote zero capability in
this instrument. The digital remote span calibration however, is
functional and accepts as input 0 V (off) or 24 VDC (on) for remote
control of span calibration. (See Remote Calibration Protocol below.)
See Table 3-5 for pin connections.
Zero: Not implemented
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.
Table 3-5: Remote Calibration Connections
Pin Function
9 + Background gas 1 (formerly remote zero)
11 – Background gas 1 (formerly remote zero)
10 + Remote Span
12 – Remote Span
40 Cal Contact
41 Cal Contact
Cal Contact: This relay contact is closed while analyzer is spanning
and/or zeroing. (See Remote Calibration Protocol below.)
Note: There is no remote zero calibration feature in this
instrument.