The difference is that a standard digital multimeter will never read the true output of a zapper that is working correctly.

The output of a zapper is a square wave with a duty cycle of 50 % ( theoretically ). Therefore, the output is at full voltage only half of the time. The meter avereages the reading so that a zapper that has a peak output of 9 volts will read approximately 4.5 volts on a multimeter. If it reads 9 volts then the output is not correct and is an indication that the zapper is stuck in the high output condition ( not oscillating ). NOTE: some meters costing hundreds of dollars can read peak voltage but this is very rare.

The original 555 timer used in the original HC zapper only outputs 7.5 to 8 volts peak on a fresh 9 volt alkaline or heavy duty battery.

We use a newer timer that produces 9.4 to 9.6 volts on a fresh 9 volt alkaline or heavy duty battery.

Rechargeable 9 volt batteries only produce 7.2 volts or 8.4 volts depending on the chemistry.

zappers

The difference is that a standard digital multimeter will never read the true output of a zapper that is working correctly.

The output of a zapper is a square wave with a duty cycle of 50 % ( theoretically ). Therefore, the output is at full voltage only half of the time. The meter avereages the reading so that a zapper that has a peak output of 9 volts will read approximately 4.5 volts on a multimeter. If it reads 9 volts then the output is not correct and is an indication that the zapper is stuck in the high output condition ( not oscillating ). NOTE: some meters costing hundreds of dollars can read peak voltage but this is very rare.

The original 555 timer used in the original HC zapper only outputs 7.5 to 8 volts peak on a fresh 9 volt alkaline or heavy duty battery.

We use a newer timer that produces 9.4 to 9.6 volts on a fresh 9 volt alkaline or heavy duty battery.

Rechargeable 9 volt batteries only produce 7.2 volts or 8.4 volts depending on the chemistry.

zappers

Thanks Hermit for the useful info. I will have to try |Maplins Electronics as I live in the UK for a Digital Multimeter.

Actually, this type of frequency meter often does not work as it expects a sine wave. The digital square waves often give erroneous readings.

I have about 15 different multimeters in our lab along with several oscilloscopes, digital frequency counters, etc.

Only one of the DMMs gives even a reasonable reading for frequency.

parasite zapper