Frequently asked questions:

Does the instrument need to be “warmed-up” before use?

No. It is ready to go instantly when turned on.

What sensor technology is used in Reliable Instruments M3 mercury vapor meters?

The sensor is a patented gold film surface chemistry transducer.

It consists of a thin film of gold on a ceramic wafer about ½ by 1 inch. The ceramic also has a gold film heater on the back side which is used to remove adsorbed mercury from the active surface. This process is called regeneration.

How does the sensor work?

The instrument measures the electrical resistance of the gold film. As mercury adsorbs to the gold it raises the resistance slightly. This change in resistance has been calibrated to correspond to a known concentration of mercury vapor during the calibration process.

Why is sensor regeneration necessary?

As the sensor is exposed to mercury vapor, some of it adsorbs onto the sensor in a process similar to condensation of water vapor on a cold surface. Each time the sensor “sees” mercury, the adsorbed load increases a little, and the sensitivity of the sensor decreases a little. At some point it is necessary to remove all the adsorbed mercury to restore full sensitivity. This is done by heating the sensor to a carefully controlled temperature which boils off the adsorbed mercury. The instrument will prompt the operator as regeneration is needed.

Do I need 120 volt power to regenerate the sensor?

No, all regeneration is done using internal battery power. Some competitors claim to have this feature, but they do not.Their user manual clearly says you have to plug in house power to regenerate. This is awkward in the field.

Why does the instrument have multiple ranges?

At very low concentrations of mercury vapor (below about 20 micrograms per cubic meter) it takes a long time to collect enough mercury on the sensor to get an accurate reading. For this reason, a range that samples for 30 seconds is provided.

At action levels (for example 50 micrograms per cubic meter) a sufficient sample is obtained in seven seconds. This is the normal or default operating range.

At higher (dangerous) levels so much mercury adsorbs on the sensor that the sensor capacity is used up in a few samples so a shorter sampling time of two seconds is used.

At saturation levels (10 to 20 milligrams per cubic meter) an even shorter sample of ½ second is used.

The instrument prompts the operator to change ranges as appropriate.

Does the sensor respond to methyl mercury?

The instrument is designed to measure, and is calibrated metallic mercury (Hg0). The sensor does respond somewhat to mercury compounds like methyl mercury but the relative response is unknown and not calibrated. We elected not to explore this application because of the hazards of this material.

Does the sensor respond to anything other than mercury?

Yes, the gold film responds strongly to some acidic gases such as HCl, H2S, and related compounds. To prevent interference from these materials an acid gas filter (AGF) is built into the instrument.

If the filter is in good condition there is no instrument response to any of these interfering gases. The filter does absorb CO2 from the atmosphere, so it is replaced annually as part of the annual calibration.

My instrument tells me the battery has failed. What should I do?

The instrument has an extensive set of battery diagnostics built in. This is to prevent any possible danger to the operator due to battery failure. Never try to charge a failed battery. Contact the factory for pricing of a replacement battery. Return the instrument to the factory for battery replacement and proper disposal of the failed battery.

Why does the charger stop charging at 80%? Shouldn’t it go to 100%?

Research has shown that this type of battery has a much longer life if the charge state is kept below 80% and above 20% at all times. Because the batteries are expensive, we elected to limit the charge to preserve the life of the battery.

Why do I get very high readings around a tiny bit of spilled mercury?

Mercury has a high vapor pressure at room temperature. It also has a high surface tension, so spilled mercury forms lots of tiny spheres and disperses into tiny cracks and crevices. Each one has a relatively large surface area which is evaporating mercury constantly. Since mercury is a neurotoxin, it is important to find and clean up spills safely, using proper hazmat gear and respirators.

Can I rent a unit to take care of a spill situation?

Yes, rental units are available from the factory at very economical rates. Weekly and monthly plans are available. Scientific equipment rental agencies also have units for rent.

Can I read the user manual before I buy one?

Yes, send an email to requesting a pdf copy of the user manual.