For this transmitter, the relationship is described by the following equation. The 60,000 relates to measurement units in
volume/min. Measurement units in seconds, hours or days would require a different numerator.
60,000
K factor
Full ScaleUnits
=
A practical example would be if the MAX RATE for the application were 400 gpm, the Kfactor (representing the number of
pulses accumulated needed to equal one gallon) would be:
60,000
150
400
Pulses Per Gallon
gpm
K factor
= =
If the frequency output is to be used as a totalizing output, the transmitter and the receiving instrument must have identical
Kfactor values programmed into them to ensure that accurate readings are being recorded by the receiving instrument.
Unlike standard mechanical transmitters such as turbines, gear or nutating disc meters, the Kfactor can be changed by
modifying the MAX RATE flow rate value. See “KFactors” on page 42.
There are two frequency output options available:
• The Turbine Meter Simulation option is used when a receiving instrument is capable of interfacing directly with a
turbine transmitter’s magnetic pickup. The output is a relatively low voltage AC signal whose amplitude swings above and
below the signal ground reference. The minimum AC amplitude is approximately 500 mV peak-to-peak. To activate the
turbine output circuit, turn SW4 OFF.
0
500 mV
p-p
Figure 28: Frequency output waveform (simulated turbine)
• The Square-Wave Frequency option is used when a receiving instrument requires that the pulse voltage level be either
of a higher potential and/or referenced to DC ground. The output is a square-wave with a peak voltage equaling the
instrument supply voltage when the SW3 is ON. If desired, an external pullup resistor and power source can be used by
leaving SW3 OFF. Set SW4 to ON for a square-wave output.
0
+V
Figure 29: Frequency output waveform (square wave)
Inputs/Outputs
Page 28 April 2016TTM-UM-00369-EN-03
To Next Page
Loading...
