Contrec 515 – FA01

Add/Subtract Flow Computer - 2 Channel Input (Volume)

The 515 FA01 application pack is an add or subtract flow computer that is tailored specifically for volume measurement.

It can perform either addition or subtraction on two frequency inputs or on two analog inputs.

The flow computer is suitable for accepting signals directly from flowmeters or for collecting retransmitted signals from other flow computers providing a resultant rate and total. The instrument displays the flow rate and total for each channel as well as the result.

The frequency input is compatible with a wide range of frequency signals, including millivolt signals, reed switches, Namur proximity switches and pulse trains via its smart front panel program selection. The analog input can be scaled and have filtering, non-linear correction and cutoff points applied to the signal.


For frequency inputs the calculation of totals are exact as the instrument collects all pulses detected on each channel.

Channel total = pulses/k-factor

The flow rates are derived from an accurately measured frequency:

Channel flow = frequency/k-factor

For analog inputs, to derive the flow rate, the analog input is normalised to a value (A) between 0 and 1.

Channel flow = (Vfmax – Vfmin) A + Vfmin

Channel total = (channelflow. Δt)

The resultant values are then:

ADD result = channel 1 + channel 2

SUB result = channel 1 – channel 2