Extech Instruments HD755-NIST User Manual page 5

Zero Adjust and Offset function
The unit must be kept in the upright position when ZEROING or when taking measurements. To
ZERO the meter: Before use and without fittings attached to the meter, press and hold the HOLD
button for 3 seconds or until the display shows all zeroes.
To OFFSET meter readings: Press the DIF button while taking a measurement. Subsequent
readings will represent the difference between the current measurement and the measurement
that was on the display when the DIF button was pressed. . Press the DIF button again to exit the
OFFSET function.
MIN‐MAX‐AVG Mode with Elapsed Timer
The RECORD function records a single maximum (MAX), minimum (MIN), and average (AVG)
readings with a time stamp. The elapsed timer is displayed on the lower right‐hand corner of the
LCD and informs the user of the time a MAX or MIN reading was recorded.
1. Press the RECORD button once. The REC indicator will appear on the display and the
displayed elapsed timer will start (HH:MM:SS format [hours:minutes:seconds]).
2. Press the RECORD button again to view the highest (MAX) reading recorded since the
RECORD button was first pressed. The MAX indicator and maximum reading will appear on
the display. The elapsed timer will show the time of the MAX event.
3. Press the RECORD button again, the MIN indicator and the minimum value will appear on
the display. The elapsed timer will show the time of the MIN event.
4. Press the RECORD button again, the AVG indicator and the average value will appear on the
display. The elapsed timer will continue to run.
5. To return to normal operation, press and hold the RECORD button until the display
indicators REC, MAX, etc. switch off.
Note that in the RECORD mode, the backlight and the power buttons are the only available
functions. The Min, Max, and AVG data cannot be exported to the PC.
PC Interface
The meter has a built‐in USB port for use with the Manometer Data Acquisition software. The
software allows the user to view, record and print readings from the HD755 while it is connected
directly to a PC. Refer to the documentation included with the software for complete details.
Displayed Error Codes
The following codes are displayed when the meter encounters an error.
ERR 1: Pressure input exceeds specified limits
ERR 2: Pressure input is too low to read
ERR 3: The Differential Pressure input exceeds specified limits
ERR 4: The Differential Pressure input is too low to read
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