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OPERATION
Once set up, the operation of the LH200 involves only three control signals, an ENABLE signal from the PLC
or sequencer to start the test cycle, a STROBE output signal to trigger the flash illuminator, and a RESULT
output signal to report the outcome of the test to the PLC.
In general terms, an inspection cycle comprises the following steps:
1. An enable signal is sent to the LH200 to begin the test cycle.
2. The LH200 takes 128 readings and averages them as a dark reference.
3. The LH200 asserts the STROBE signal to trigger the flash illuminator.
4. The LH200 captures the peak signal sensed during the flash.
5. The LH200 assesses the dark level and peak value and reports a leak if either or both signals
exceed their respective test limits.
The test cycle is described in greater detail later in this document. See TEST CYCLE DETAIL
USER INTERFACE
The LH200 may be connected to a terminal, laptop, or personal computer for user access to configuration
parameters. Set the serial connection parameters to 34800 baud, 8 data bits, 1 stop bit, no parity and no
handshake. When the connection has been established, enter a question mark, "?" to display the command
menu:
Commands:
A – Auto Adjust, 0/1
B – Bias
C – Cal Offset
F – Free Run
D – Dark Limit
G – Gain
S – Spread Limit
L – Leak Limit
R – Reports
V – Version
? – Menu
Note on Parameters:
In most user applications, it will not be necessary to adjust the available parameters. The default values were
determined by testing in a typical, real world installation. However it may be necessary to adjust the Leak
Limit and Dark Limits based on ambient light intrusions and desired leak reject levels.
A
- Auto Adjust
The "A" command allows the user to enable and disable the auto adjust feature. "A" has only two values, 0
and 1. Zero disables the auto adjust feature and 1 enables it. The default is 1, enabled.
The auto adjust mechanism monitors the average of the internal bias readings taken during the dark period
of the test cycle and adjusts an internal offset to maintain the dead-band as specified by the "B" setting. This
insures constant sensitivity through a wide range of temperatures. It is recommended to leave this setting
enabled for most installations.
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