Teledyne 300M - Manual (Page 45)

Teledyne API Model 300M CO Analyzer Instruction Manual, 04033, Rev. A
3.6 Remote Zero/Span Check or Adjustment
(Contact Closure)
In addition to adjustment via the front panel buttons, the analyzer can be adjusted by means of
two contact closures called EXT_ZERO_CAL and EXT_SPAN_CAL. (See Figure 1-3 for the
location of the terminals for connection of the contacts on the rear panel.) The CPU monitors
these two contact closures every 1 second and looks for a positive transition (i.e. 0
→ 1) on
either signal. If a positive transition occurs on EXT_ZERO_CAL, the CPU will perform a zero
check. If a positive transition occurs on EXT_SPAN_CAL, the CPU will perform a span check.
When a negative transition i.e. 1
→ 0) is detected, the CPU will go into hold-off.
Also, if a positive transition occurs on either signal while the M300M is in zero, span check or
hold off, it will immediately switch to the specified mode. For example, if the analyzer is in zero
check and a positive transition is detected on EXT_SPAN_CAL, then the instrument will
immediately go into span check. To perform a zero check followed by a span check, first
generate a positive transition on EXT_ZERO_CAL, and then when you want to do the span
check, generate a positive transition on EXT_SPAN_CAL.
The remote calibration signals may be activated in any sequence, providing a virtually unlimited
number of calibration types.
Remote adjustment is similar to automatic Z/S checking in that if dynamic calibration is enabled,
the internal CO formulas will be modified following calibration. To enable or disable
adjustment, press SETUP-MORE-VARS and press NEXT until the variable DYN_ZERO or
DYN_SPAN is displayed. To change the setting, toggle the value between OFF - ON and press
ENTR to store the new value or EXIT to leave the value unchanged.
NOTE
Teledyne API recommends that contact closures remain closed at
least
10 minutes to allow for an accurate average zero or span value
to be established.
NOTE
Remote zero and span adjustment alter the formulas used to
compute the carbon monoxide readings if DYN ZERO or
DYN SPAN are enabled.
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