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Application: how the pulse count module works – Sensaphone SCADA 3000 Users manual User Manual

Page 259

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Chapter 24: Pulse Count Module

to digital logic signals, follow the polarity markings shown at the terminal strip. Note that if

the sensor is located far from the Pulse Count Module or if you are running cable in an electri-

cally noisy environment, you should seriously consider using shielded cable. This will shield

the signal from electrical interference, thereby preventing false readings and/or damage to the

module.

Figure 8: Module Input wiring

Adjusting the Trimpot (Filtering)

Each channel of the pulse count module has an adjustable low-pass filter. This filter is used

to prevent errors generated by the bounce from slow-moving switches. The filter cut-off fre-

quency is adjusted by turning the trimpot (as shown in Figure 9) to the appropriate position.

The trimpot range is scaled from 0 to 10. Adjust the trimpot based on the maximum pulse fre-

quency expected in your application. The table below will help you select the correct position.

Maximum

Pulse Frequency Trimpot Position

200 Hz

0

350 Hz

2

1

2

700 Hz

5

1200 Hz

7

1

2

10,000Hz

10

Figure 9: Trimpots, with Pot 1 set at 0, Pot 2 at 2.5, Pot 3 at 5, and Pot 4 at 10

APPLICATION: HOW THe PULSe COUNT mODULe WORKS

The two main uses for the Pulse Count Module are:

a) to measure and record flow rates. The liquid flow rate sensor operates like a pad-

dlewheel, and each rotation causes an electrical pulse.

b) to measure RPM. Industrial generator or motor activity is usually measured in

RPMs.

The SCADA 3000 Pulse Count Module splits incoming data into four channels of accumulated

pulse, and four virtual channels measuring the rate of pulses, thus generating a total of eight.

Thus you can receive two different measurements from a single input.