Measurement Parameter

Control Checks

Control Limits

Corrective Actions*

pH

Measure buffer pH at least following every other measurement.

Buffer measurements within 0.2 units of actual values.

Recalibrate pH meter; check batteries and probe condition.

Electrical Conductance

Measure standard daily.

±10 percent of actual value

Replace or replatinize probe; verify that meter zeros and redlines properly; check batteries.

Temperature

Check measurement.

±1ºC

Replace thermometer or correct temperature readings.

Volatile organics (PID)

Measure standard gas at least daily.

±5 percent

Replace dust filter; clean lamp; check battery.

Explosive gases

Measure calibration standard daily; test periodically in known explosive environment (gas tank) and check zero in clean environment.

Adjust meter to read exact standard value.  Control limit for fresh air is ±1 percent.

Recalibrate meter; check battery; replace sensor.

Water level (water level indicator)

Measure weekly against tape measure when in regular use.

±0.02 feet

Replace meter tape.

* Required if control limits not achieved.