FC 103 - Pulse Input / Frequency

The pulse input/frequency function code interfaces a controller to a selected channel of an IMDSM04 Pulse Input Module.  The IMDSM04 module conditions, converts and processes pulse inputs into analog signals. It has eight inputs that can be processed in three modes: period, frequency and totalization. Function code 103 configures a signal to output a frequency value. Function codes 102 and 104 process signals in the period and totalization modes, respectively. Function code 109 processes the duration of the input pulses. Each input channel must have only one pulse input block configured.

 

Outputs:

Blk

Type

Description

N

R

Frequency (Hz) X gain

N+1

B

Frequency high alarm:

0 = no alarm

1 = high alarm

N+2

B

Frequency low alarm:

0 = no alarm

1 = low alarm

N+3

B

I/O module communication status:

0 = good

1 = bad

 

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

0 - 63

Expander bus I/O module address of IMDSM04

S2

N

1

I

1 - 8

Selected channel

S3

N

0

B

0 or 1

Pulse trigger level:

0 = low to high transitions

1 = high to low transitions

S4

N

1

I

1 - 6

Expected period range:

1 = 0.15 mHz - 10 mHz, + 0.01 mHz

2 = 1.5 mHz - 100 mHz, + 0.1 mHz

3 = 15 mHz - 1.0 Hz, + 1 mHz

4 = 0.1 Hz - 6.55 kHz, + 0.1 Hz

5 = 1.0 Hz - 50 kHz, + 1.0 Hz

6 = 10.0 Hz - 50 kHz, + 10.0 Hz

S5

Y

1.000

R

Full

Gain

S6

Y

9.2E18

R

Full

High Alarm Value

S7

Y

-9.2E18

R

Full

Low Alarm Value

S8

Y

0.000

R

Full

Spare

 

 

 

103.1   Explanation

 

In the frequency mode, a counter records the number of input pulses or cycles that occur per second. The expected frequency range is configurable with S4. There are six frequency ranges available with range one having the highest resolution (+ 0.15 millihertz) but smallest span, compared to range six with the lowest resolution (10.0 hertz) but largest span. The pulse trigger transition can be configured to respond to either the rising or falling portion of the signal with S3. The determined frequency is scaled with S5 and tested against specified high and low alarm values specified by S6 and S7.

 

103.1.1   Specifications

 

S1 - SLVADR

Expander bus I/O module address of the IMDSM04 module. Valid addresses are zero through 63.

 

S2 - CHNL

Identifies the input channel being monitored. IMDSM04 modules have eight input channels. Refer to the IMDSM04 Pulse Input Module product instruction to identify the channel associated with each input.

 

S3 - PTRIG

Defines the type of signal transition that triggers the counter response.

0 = response on low to high transitions

1 = response on high to low transitions

 

S4 - RANGE

Defines the range within which the frequency of the input pulses is expected to fall. There are six frequency ranges shown below. Resolution decreases from range one to six.

1 = 0.15 millihertz to 10 millihertz, + 0.01 millihertz

2 = 1.5 millihertz to 100 millihertz, + 0.1 millihertz

3 = 15 millihertz to 1.0 hertz, + 1.0 millihertz

4 = 0.1 hertz to 6.55 kilohertz, + 0.1 hertz

5 = 1.0 hertz to 50 kilohertz, + 1.0 hertz

6 = 10.0 hertz to 50 kilohertz, + 10.0 hertz

If the frequency goes above the expected range (ranges one through six), the output stops with the last valid frequency and the I/O module communication status becomes a logic 1. This also occurs on ranges one, two and three if the frequency goes below the expected range.

 

S5 - K

Defines the gain multiplier. Gain scales the output to a useful value.

 

S6 - HALRM

High alarm output (N+1 equals logic 1). Specification S6 is dependent on the values chosen with S4 and S5.

Output = frequency(gain)

 

S7 - LALRM

Low alarm output (N+2 equals logic 1). Specification S7 is dependent on the values chosen with S4 and S5.

Output = frequency(gain)

 

S8

Reserved.

 

 

103.1.2   Outputs

 

N

Real value representing the frequency (in hertz) times the gain.

 

N+1

High alarm.

0 = no alarm

1 = high alarm

 

N+2

Low alarm.

0 = no alarm

1 = low alarm

 

N+3

I/O module communication status.

0 = good

1 = bad

 

The I/O module is marked bad if:

• There is an illegal I/O module response or no I/O module response.

• No pulses have been received yet.

• The frequency exceeds the expected range.

• The frequency goes below the expected range for S4 equal to one, two or three.