Bacharach H25-IR - Manual (Page 41)

H25-IR Operation
Instruction 3015-4342 35
4.4 PCHK
(Atmospheric Pressure CHecK)
The instrument maintains its accuracy under varying atmospheric conditions by performing an atmospheric
pressure check once every hour, or immediately after calibration (refer to Section 2.5.7 PCHK Mode.) When a
PCHK is performed, the unit beeps once, the pump stops, a valve opens exposing the pressure sensor to the
atmosphere, and “PCHK” appears at the bottom-right of the display. During this time the instrument measures
the current atmospheric pressure, and then uses this value along with the current temperature and the ideal gas
law to compute the gas level. When the pressure check is complete (approximately 5 seconds), the unit beeps,
the valve closes, and the pump restarts.
4.5 RS-232 Communication
The RS-232 connector located on the rear of the instrument (refer to Section 1.7.2 Rear View) is used to flash
the instrument’s memory. Refer to Section 5.3 Flashing Memory.
Additionally, leak rate data can be output from the port as ASCII text in two formats.
4.6 Serial Output Types
Text Packet
 When TEXT PACKET is selected, a 16 character ASCII string is output approximately 10 times per
second. The string is formatted as follows:
<STX> XX.X,-p.pp<ETX>cc
 XX.X is the leak rate as displayed on the front panel, -p.pp is the internal pressure drop in PSI and cc is
a two byte checksum.
Text Only
 When TEXT ONLY is selected, a 10 character ASCII string is output approximately 10 times per
second.
 The string is formatted as follows:
XX.X,-p.pp <CR><LF>
 XX.X is the leak rate as displayed on the front panel and –p.pp is the internal pressure drop in PSI. CR
and LF stand for carriage return and line feed. This option is convenient for capture to file using
Hyperterminal or similar software.
Oz/yr
R134A
SETUP
PCHK
Pressure check in progress
SERIAL OUTPUT TYPE
NONE
TEXT PACKET
TEXT ONLY
<CLOCK
PCHK MODE
SERIAL OUTPUT
<PROBE BUTTON