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imc C-SERIES - Manual, Version 4 R 3 - 2018-10-19

49Measurement types

Pulse Time

The point in time at which the edge is located within the sampling interval is determined. This

information is needed by some functions in imc Online FAMOS, e.g. for determining the course of the

RPMs from a pulse signal: OtrEncoderPulsesToRpm.

The measurement variable Pulse Time refers to phase-based data which is only relevant to special

applications (particularly order-tracking analysis). It is required for subsequent online calculations. It

represents the time between the last detected (asynchronous) pulse and the (synchronous) sampling

time at which the counter readings were sampled and evaluated. The unit associated with this

variable is called Code.

Note

The mode Pulse Time depends on the sampling rate. For all ENC-4 types, the entry is visible only if

the sampling rate is equal or smaller 1ms. For HRENC-4 the sampling rate must be equal or less

100µs.

PWM

Pulse width modulation (PWM) is a type of modulation in which a technical variable (e.g. electrical

current) switches between two values. In the process, the duty cycle ratio is modulated at constant

frequency. PWM is also known as pulse duration modulation (PDM).

A good illustration of this modulation type would be a switch used to continually switch a heater on

and off. The higher the ratio of the on-time to the off-time, the higher the average heating power is.

Measurement of PWM can not be performed directly with the device software. However, if the

frequency is known, it is possible to perform it indirectly by time measurement with the following

settings:

The ratio is the Duration of HIGH (signal) level over the Period duration.

The Duration of HIGH (signal) level is obtained by means of a time measurement from positive to

negative (signal) edge.

The Period duration is the inverse of the frequency, which must be known.

PWM= t

pulse

Period duration

* 100% or t

pulse

* f * 100%

Example:

f= 50Hz, Pulse duration = 10ms

Scaling: t

pulse

* f * 100%/ s = 5000%/s

at 10ms: 0.01s*5000%/s= 50%

IMC C SERIES User Manual

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