Question 1

What power supply do I need for Options W2 and W3?

Accepted Answer

Both W2 and W3 require an external 24 VDC power supply with a minimum capacity of 25 mA. The power supply is not included with the meter — it must be user-supplied. Connect the positive terminal to Terminal 2 (+) and the negative terminal to Terminal 1 (–) on the transmitter board.

Question 2

Can I connect multiple receiving devices to a single W2 or W3 transmitter?

Accepted Answer

Yes. Additional receiving devices (DCS indicators, digital readouts, data loggers) can be connected in series in the current loop. However, the total loop impedance of all devices combined must not exceed 650 Ω for W2/W3 or 350 Ω for RW3 at 24 VDC. Exceeding the maximum load impedance will cause the output to saturate and readings will be inaccurate.

Question 3

What is the difference between Option W2 and Option W3?

Accepted Answer

Both options are electrically identical — they use the same solid-state strain gage transmitter board and produce the same 4–20 mA DC output. The only difference is that Option W2 retains the local mechanical analog indicator (the float and scale), while Option W3 omits it. Choose W3 when the local readout is not needed and you want a cleaner installation.

Question 4

Is the transmitter output isolated from the process fluid?

Accepted Answer

Yes. The solid-state strain gage measures differential pressure across the meter orifice through the meter body — there is no direct electrical contact with the process fluid. The transmitter board is located inside the meter enclosure, separated from the wetted components.

Question 5

Why does the output need to be linearized in the receiving device?

Accepted Answer

The W2 and W3 transmitters output a signal that is linear with differential pressure (DP), not with flow rate. Because flow rate is proportional to the square root of differential pressure (Q ∝ √DP), the mA output follows a quadratic relationship with flow: I = 16Q² + 4.00. Your PLC, DCS, or digital readout must apply a square-root extraction to convert the mA signal to a linear flow reading.

Question 6

What is the output at 0%, 50%, and 100% of full scale flow?

Accepted Answer

At 0% flow: 4.00 mA. At 50% flow: 8.00 mA (not 12 mA — because the output is quadratic, not linear). At 100% flow: 20.00 mA. Use the formula I = 16Q² + 4.00 (where Q is the decimal fraction of full scale) to calculate the expected output at any flow rate.

Question 7

What does the RW3 option add compared to W2/W3?

Accepted Answer

The RW3 is a combined 2-wire loop-powered transmitter and digital display. It accepts the 4–20 mA signal from a W2 or W3 transmitter and displays both instantaneous flow rate and totalized flow on a local digital readout. It also provides a scaled pulse output for remote totalization. The RW3 requires 24 VDC and has a maximum loop impedance of 350 Ω.

Question 8

My meter was factory calibrated — do I need to recalibrate it in the field?

Accepted Answer

No — all meters are factory calibrated before shipment. Field calibration is only necessary if you have reason to believe the meter is reading incorrectly (e.g., after a repair, or if the meter was damaged in transit). Do not adjust the span potentiometer unless you have proper test equipment and can establish a known steady flow rate close to full scale.

Question 9

How do I check and adjust the zero (4 mA) output?

Accepted Answer

Connect a multimeter in series with the current loop. Pressurize the pipeline to operating pressure with no flow. The output should read 4.00 mA ±0.02 mA. If it does not, adjust the zero potentiometer (labeled "Zero Pot" on the transmitter board) until the output reads 4.00 mA. This adjustment does not affect the span calibration.

Question 10

The output reads above 20 mA or below 4 mA — what should I check?

Accepted Answer

First, verify the power supply is providing 24 VDC and at least 25 mA. Then check that the total loop impedance (sum of all receiving device input resistances plus wiring resistance) does not exceed 650 Ω for W2/W3. If the output is stuck at 4 mA with flow present, check for a blocked orifice or a failed strain gage — contact Northeast Controls for service.

Question 11

Can I retrofit a W2 or W3 transmitter to an existing meter?

Accepted Answer

Yes. Transmitter options W2 and W3 can be retrofitted to most existing Flo-Gage meters in the field. Contact Northeast Controls with your meter model number and serial number to confirm compatibility and obtain a retrofit kit. Factory installation is also available — return the meter with an RMA number.

% Full Scale	Current Output (mA)
20%	4.64
30%	5.44
40%	6.56
50%	8.00
60%	9.76
70%	11.84
80%	14.24
90%	16.96
95%	18.44
100%	20.00

Wiring & Calibration
Transmitter Options W2 & W3

1. Installation & Wiring

Option W2

Option W3

Transmitter Operation

Power Requirements

Startup Procedure

Figure 1 — Connection Diagram

Adjustment Potentiometers

Figure 2 — Loop Impedance vs. Power Supply Voltage

2. Field Calibration (4–20 mA DC)

2.1 Test Equipment

2.2 Procedure

Warning

Zero Calibration

Span Calibration

% Full Scale to Current Output

W2 & W3 Transmitter FAQ

Wiring & Power

Signal & Linearization

Calibration & Troubleshooting

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Wiring & CalibrationTransmitter Options W2 & W3