MUNI User’s Guide
12
5.4 Calibration and Bump Testing
Use this menu to perform zero or span calibration for one or more sensors, bump test the sensors
and alarms for function, and change the span gas concentration.
The MUNI should be calibrated on the first day of use and at regular intervals not to exceed 180
days, depending on use and exposure to particulates, contaminants and sensor poisons. A daily
bump test should be performed to ensure a functional response of all sensors and alarms.
•
BUMP TEST
is defined as a brief exposure to sensor gases, typically 10-20 seconds, just
long enough to indicate that the sensors are responsive and the alarms are functional, without
concern for a quantitative measurement.
•
CALIBRATION
is defined as exposing the sensor(s) to a known concentration standard gas
for the full calibration time (typically 30-60 seconds, but longer for HCN) and setting the
reading of the sensor(s) equal to the concentration of the calibration gas.
Calibration intervals and bump test procedures may vary due to sensor type, ambient conditions,
local regulations and/or the user’s company policies.* Automatic reminders for calibration and
bump tests can be set up in the CAL? Menu or using the mPower Suite software (see Section
6.1). When a calibration or bump is due, a small icon is displayed next to the sensor name:
for Cal and for Bump as shown below:
Calibration is also required if:
•
The sensor has failed in a previous bump or calibration
•
The sensor module has been replaced with one whose calibration is overdue.
•
A new sensor is installed.
For more on calibration frequency see Tech/App Note 3 “How Often to Calibrate Gas Detectors”.*
* The calibration frequency must be defined by the user’s company policy because each application is different and
may cause a sensor’s sensitivity loss for various reasons out of mPower’s control, such as liquids, dirt or corrosion
preventing gas from reaching a sensor, or exposure to chemicals that poison a sensor’s function. Exotic gas sensors
tend to need more frequent calibration than common O
2
, LEL, CO and H
2
S sensors. In general we recommend a
bump test before each day’s use to test sensor response and alarm function. A calibration check can be performed
by applying a known concentration gas to see if the sensors still respond within typical limits. Cal check intervals
can be increased as the user gains experience in the application. If a bump or cal check fails, the instrument should
be given a full calibration. We recommend no more than one month between full calibrations, but this can be
extended for up to 6 months if company policy allows.
