Zero Adjustment & Calibration

 

The differential pressure is measured with a differential pressure transducer in the eFlo-H and eFlo-L.  This sensor does not measure absolute pressure (i.e. supply or line pressure), it only measures a difference in pressure on each side of the orifice plate in the meter.  The diaphragm in the transducer is very sensitive to its orientation with respect to gravity.  After shipping and installation, the diaphragm in the transducer may have shifted slightly.  This can cause a flow reading to display on the meter when the valve is closed and the meter set point is zero.  This is called zero drift. The meter must be zero’ed when you observe zero drift.  There are two methods of zeroing the meter depending on the amount of zero drift.

 

There is an adjusted mA input based on the pressure transducer measurement when the flow rate is zero and supply pressure is applied to the meter. This mA value is known as the zero value. Ideally, the zero value will be 4.00 mA or slightly below.

 

• In a situation where pressure is applied to the inlet, no flow is present, and the mA reading is less than 4.25 mA or greater than 3.75 mA, a Zero tare in the field will often be required. 

• If the mA zero value reading is greater than 4.25 mA or less than 3.75 mA, a Zero calibration is required. 

 

The Zero tare and Zero calibration procedures are provided in Appendix 2.  This procedure will require the use to be familiar with the keypad or touchscreen in order to navigate through the meter and perform the function(s).

 

IMPORTANT!   For best long term results, it is recommended that pressure be maintained on the flow meter at all times. Pressure can be maintained when the shut off solenoid/valve is downstream from the outlet of the meter. This will ensure long term calibration and accuracy.