GSE 60 SERIES Technical Reference Manual page 465

simply key in a new value and press [ENTER]. [CLEAR] may be
pressed to reset a value to zero.
'P T ' D
HS M ETAILED
The elapsed amount of high or low time (measured with a resolution of
1.91 µs) during a specified number of pulses (i.e. periods) is divided by the
incoming number of periods signal to determine the average high or low
time for those pulses.
The Phase Time measurement is intended for use with input signals that
have a fixed frequency. Therefore the number of pulses may be
determined based upon choosing a reasonable balance between response
time and accuracy.
'P T ' E
HS M XAMPLE
As an example, let us consider a PWM (Pulse Width Modulated) input
signal with a fixed frequency of 10 kHz that is being provided by a tank
level sensor. We will assume that the level of the tank is proportional to
the high time of the PWM signal. Then the value of the time measured by
the 'PhsTm' function is proportional to the tank level.
If we want a new calculated value 60 times per second, then the number
of pulses to be used for each measurement may be calculated as follows:
10 000 , Cycles
Second
60 Measurements
Second
Since the High time is proportional to the parameter being measured, set
P861 to 'High'.
Through the use of a scaling factor, the measured time may be converted
into a value with meaningful units for the parameter being measured.
Since the frequency is 10,000 Hz, the high time may range from 0/10,000
to 1/10,000 (0.0001) Seconds.
To determine the scale factor, divide the desired maximum value by the
phase time that will represent that value. Specifically:
MaximumDisplayedValue
CorrespondingMeasuredValue
For example,
To display the tank level as a percentage of its capacity, the maximum
displayed value would be 100 (%) and that would correspond to a phase
time measurement of 0.1 ms. Therefore, the scale factor value should be
100/0.1 = of 1,000,000.
One Period
Programmable Digital I/O 12-19
E
XPLANATION
= 166.66 Cycles (or Pulses) per
measurement. Thus set P860
to 167.
=
ScaleFactorValue
60 Series Technical Reference Manual