Only the following two H7CX-series models can be used as tachometers.
H7CX-R Tachometer
H7CX-AW Multifunction Preset Counter/Tachometer

Adjust the auto-zero time.

The default auto-zero times for each model are as follows:
H7CX-R: 999.9S
H7CX-AW: 99.9S (when used as Tachometer)

Example: A machine that outputs 1 pulse per revolution is rotating at 30 revolutions per minute. The revolutions can drop to 10 revolutions per minute.

30 revolutions per minute (30 rpm) indicates that
60 (seconds) ÷ 30 (revolutions) = 2 (seconds per revolution)
Therefore a pulse is normally input every 2 seconds.

When the rate of rotation falls to 10 revolutions per minute (10 rpm),
60 (seconds) ÷ 10 (revolutions) = 6 (seconds per revolution)
Therefore the pulse interval becomes 6 seconds.

If the auto-zero time is set to 6 seconds, it waits for the next pulse for 6 seconds, and then displays the speed at that time (e.g., 10 rpm). If there are no more inputs, the auto-zero function is activated and the display becomes zero.
If the pulse interval is longer than the auto-zero time, the auto-zero function is activated and the display becomes zero.

Applicable models: H7CX-R and H7CX-AW