Tachometer Frequently Asked Questions

The TM-3100's display and analog/BCD output signal processing flow are as follows:

[1] Periodic calculation/moving average

The input signal is repeatedly calculated periodically every 10 ms to determine the speed. If "Moving Average OFF" is selected, the current periodic calculation is used as the data. If "Moving Average 32" is selected, a moving average is calculated from the 32 most recent periodic calculation values, and the moving average value is used as the data. If the input signal frequency is high and there are multiple signals within 10 ms, the calculation is performed using the average period of the multiple signals. Also, if the frequency is low, for example, 10 Hz (period 100 ms), the periodic calculation value will change while waiting for the signal to be received. Therefore, approximately 10 data points will be the same until then.

[2] Display update process

The speed is displayed by performing an average calculation using the [1] data points for the duration of the display update time. If the setting is 1 s, the average of approximately 100 data points (1 s ÷ 10 ms = 100) will be displayed. However, the maximum number of data points for this average is 120, so if the display update time is set to 2 s or more, the average of the first 120 data points (over approximately 1.2 s) immediately after the update will be displayed. Therefore, whether the setting is 2 s or 10 s, the average number of data points is 120, but the difference lies in whether the average calculation and display update are performed at 2 s intervals or 10 s intervals.

[3] Display update analog output update process

The data [1] immediately preceding the timing of the analog output update is converted to D/A and output. If the analog output update is set to 1 s, D/A conversion is performed every 1 s. Generally, the analog output update time is set to 10 ms, and the responsiveness is adjusted using the moving average setting.

■Example Settings 1: When "Display update 1 s, Moving average OFF, Analog update time 1 s" is selected.

■Example Settings 2: "Display update 1 s, Moving average 32, Analog update time 1 s"

［4］ BCD out

The BCD output works similarly to the analog output. It outputs either the instantaneous data or the moving average value at a timing point with a 100 ms update time.

Note: If the input signal is 1 s, the same value will be output as BCD approximately 10 times (for about 1 s). In request mode, the data at the moment the request is received will be output.

［5］ RS232C

RS232C also returns instantaneous data when it receives the "RMD" command.