A frequency meter may have different meanings to people in different fields, though they are related. In electrical situations there are the vibrating reed types seen of generator power boards. These are simply connected across the mains like a voltmeter. These indicate when the mains is close to the desired frequency. They help with setting the RPM of a diesel generator. In radio and electronics applications it is more likely to be called a frequency counter. It has a digital counter, a frequency reference and a time base counter. It measures frequency by counting the input signal for a specific time. They are often able to measure time intervals too. These can be very precise, especially using precision external references. Connections. Connect to the signal to be measured as appropriate, so for lower frequencies the connection is something like an audio cable with clip leads. This can load the circuit under test. A divide by 10 oscilloscope probe is useful to reduce this loading. Frequency meters for higher frequencies like VHF, UHF and microwave often have a 50 ohm input, and are designed to be connected via a coaxial cable, terminated at the input of the instrument. There has to be an arrangement to tap power off the device being measured. Safety Precautions. The most important safety precaution is to keep the voltage or power at the input to a level that will not cause damage. The lower frequency types may have a voltage rating, and the 50 ohm types have a power rating. A suitable kind of attenuator is needed if the voltage/power is too high.
The frequency meter is used for measuring the frequency of an alternator or other equipments like variable frequency drives. It should be connected between two lines of a unit. Check for its voltage rating. The meter should be rated the same as the voltage rating of the line being measured. It could be used also for vhf and uhf frequency, digital or analog. So depending on your application, you have to specify its frequency range and voltage rating.
