I have a honeywell make Differential Pressure Transmitter connected to an orifice plate. we use this to calculate flow in our solar thermal system. Now, we had the display calibrated to output flow in gpm. The supplier is no more on talking terms with our company due to some legal hassle. We need to now find the orifice plate equation and use it to further connect the flow meter to a CR1000 data logger. Can anyone help with the calibration of the transmitter to display dp or even a calculation mechanism to find it offline?

Pressure range of transmitter 0-400inH2o or 1000 mBar. Voltage range 0.4 - 2 V DC.

Maximum flow - 7500 lit/h

 

The orifice plate bore is sized at specific 'design' conditions to produce a certain max DP at a certain max flow rate, for instance, 4,000l/hr at 100"w.c. DP

The orifice plates from our vendor are stamped with the manufacturer's name, a serial number, an inlet bore size in inches to 4 decimal places, the line size it was spec'd for and a code for the material of construction.

Every manufacturer I'm aware of provides a sheet of paper with the design criteria and the results of the flow calculation that includes a max DP value and the associated max flow value.

In order to configure your DP transmitter to give 20mA at design max flow rate for that orifice plate, you need find out the 'design' max DP value which will be the URV (upper range value) that you configure into the transmitter. In order to configure a display or a receiver device, you need to know the max flow rate associated with the URV/max DP/20mA value.

I'd do the lazy man's thing and attempt to contact the manufacturer and get the sizing sheet for the serial number on your orifice plate. In a world of pdf's and email, that has a high probability of success. But if that doesn't work, then you can download Mr. Daniel's freeware Orifice Flow Calculator bore sizing program from here

http://daniel-orifice-flow-calculator.software.informer.com/3.0/
(take out any space that the forum inserts into the URL)

and work backwards, because you know the presumed max flow (7500l/hr), the pipe line size, the orifice plate's bore size, and fluid SG so you can calculate the DP.

Somewhere you need to enable a square root extraction function so that the pressure is converted to a linear flow signal. You can square root in the transmitter or you can do it in the receiver, but do it only in one location.

The transmitter's output is a dc current signal, 4-20mA. The 0.4 - 2.0Vdc output range means that the transmitter's native 4-20mA output is being driven through a 100 ohm resistance across the input of some receiver device's analog input. That voltage could vary depending on the resistance (if connected to some other device).

The transmitter loop needs a nominal 24Vdc power supply.

 

Daniel's freeware Orifice Flow Calculator was really helpfull. thanks for sharing