Radiation Monitors and Meters

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Light

Description and Applications

The light meter is a portable unit designed to measure visible, UV, and near-UV light in the workplace. (The CTC has a UV light meter available through its loan program, ALEP.)

The light meter is capable of reading any optical unit of energy or power level if the appropriate detector has been calibrated with the meter. The spectral range of the instrument is limited only by the choice of detector.

Steady-state measurements can be made from a steady-state source using the 'normal operation' mode. Average measurements can be obtained from a flickering or modulated light source with the meter set in the 'fast function' position. Flash measurements can be measured using the 'integrate' function. (OSHA currently does not own any light meters with integrating capacity.)

Calibration

No field calibration is available. These instruments are generally very stable and require only periodic calibration. Units should be sent to the CTC for calibration.

Special Considerations

Exposure of the photomultiplier to bright illumination when the power is applied can damage the sensitive cathode or conduct excessive current.

Maintenance

Little maintenance is required unless the unit is subjected to extreme conditions of corrosion or temperature. Clean the optical unit with lens paper to avoid scratching.

Ionizing Radiation

Description and Applications

The ionizing radiation survey meter is useful for measuring radon decay products from air samples collected on filters. Wipe samples collected on a filter can also be counted with this detector, and general area sampling can be done. Several types of ionizing radiation meters are available from the CTC's loan program (ALEP).

The survey meter with the scintillation detector can be used to measure the presence of radon-decay products in a dust sample. The barometric pressure should be noted for ionizing radiation chambers.

Calibration

No field calibration is available. Periodic calibration by a laboratory is essential and should be handled by the CTC.

Nonionizing Radiation

Description and Applications

Various nonionizing radiation survey meters are available through the CTC's ALEP for measuring electromagnetic fields. The frequency ranges covered by OSHA's instruments are: 10 Hz to 300 kHz, 0.5 MHz to 6000 MHz, 6 GHz to 40 GHz, and the 2.45 GHz microwave oven frequency. These instruments are capable of measuring the electric field strength (E-field), magnetic field strength (H-field), or both depending on the instrument.

Depending on the instrument, electromagnetic field strengths from power lines, transformers, video display terminals, RF induction heaters, RF heat sealers, radio & television transmitters, microwave ovens and other sources can be measured.

Calibration

No field calibration is available. Periodic calibration by a laboratory is essential and should be handled by the CTC.

Special Considerations

Some of the instruments have an automatic instrument zeroing, other instruments may require 'zeroing' the instrument in a 'zero-field' condition. Check the manual for guidance.
Some units have a peak memory-hold circuit that retains the highest reading in memory.
Some units operate with either electric (E) or magnetic (H) field probes based on diode-dipole antenna design. Total field strength is measured at the meter regardless of the field orientation or probe receiving angle. The diode-dipole antenna design of the probe is much more resistant to burnout from overload than the thermocouple design of probes used with other meters.

Maintenance

No field maintenance is required other than replacing the alkaline batteries when needed.

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