ENMET Formaldemeter htV - Manual (Page 8)

ENMET Corporation Formaldemeter htV
6
5.0 Maintenance
W ARNING : Please read this section thoroughly before attempting to check or adjust calibration. Users are strongly advised to
familiarize themselves with the instrument before attempting to adjust the calibration and should follow the instructions
carefully.
5.1 General Information
Check calibration regularly
Sensor sensitivity can change very gradually with time, periodic recalibration may be required. It is advisable to check
calibration regularly to ensure that the instrument is functioning correctly.
A quick calibration check can be carried out by drawing a formaldehyde vapor sample of known concentration into the
instrument’s sensor and noting whether the displayed reading agrees with the expected concentration value.
The Formaldemeter ™ htV is supplied complete with a formaldehyde calibration standard and a thermometer, which are
essential components for checking and adjusting calibration.
5.2 The Formaldemeter
™ htV
Calibration Standard
The Formaldemeter
™ htV Formaldehyde Calibration Standard consists of formaldehyde absorbed on a solid substrate in a
glass tube from which a headspace vapor sample can be drawn. Each standard is carefully manufactured to a high tolerance.
5.2.1 Effect of temperature
The concentration of formaldehyde vapor generated in the calibration tube varies with temperature and for this reason, a
thermometer and temperature/concentration table is supplied.
Handle the calibration standard as little as possible, and only by the yellow end caps to avoid heating the
tube.
5.2.2 Temperature equilibration
Before using the standards, they should always be allowed to stabilize within the recommended temperature range of 15 – 29°C
for at least 1 hour.
5.2.3 Standard life
Each standard has a capacity for 100 samples or a life of six months (whichever occurs sooner) and it must not be used after the
indicated expiry date. New calibration standards can be ordered from your local distributor.
5.3 Calibration Check Procedure
5.3.1 Temperature equilibration
Place the instrument, thermometer and calibration standard together in a place where the temperature is stable for at least one
hour before commencing the calibration check procedure to allow thermal equilibration.
5.3.2 Sensor check
Before carrying out a calibration check, the sensor must be clear of formaldehyde vapor from any previous samples. When the
sensor is clear, the display will show:
3 seconds after power on.
If the display shows flashing for longer than 5 seconds, then the sensor is not ready to take a sample. Switch the
instrument off and allow it to recover for a few minutes.