WIKA Pressure Gauges: 8 FAQs Engineers Ask About Differential, Diaphragm & Calibration Tools

Why do you need an instrument review in the first place?

When I first started specifying pressure instruments for process lines, I assumed any gauge with a decent brand name would do the job. It took me four years and roughly 200 order reviews to realize that the right gauge is more about the application than the brand — but the brand determines how long that gauge stays accurate. This article covers the questions I get asked most often about WIKA’s differential pressure gauges, diaphragm gauges, and the tools you’ll need to verify them (including multimeters like the Fluke 289). Let’s jump in.

1. What’s the difference between a differential pressure gauge and a regular pressure gauge?

A standard gauge measures the difference between the process pressure and atmospheric pressure. A differential pressure (DP) gauge measures the difference between two process points — for example, across a filter or an orifice plate. WIKA’s DP gauges (series 732.51, for instance) use two separate pressure chambers with a single sensing element. The reading tells you the pressure loss, which can indicate clogging or flow rate. What people get wrong: they think a DP gauge is just two pressure gauges wired together. It’s not. The mechanical design is completely different — single capsule, one pointer. Trying to calculate DP from two separate gauges introduces parallax and accuracy errors that can cost you a $22,000 redo (yes, I’ve seen it).

2. When should I choose a WIKA diaphragm pressure gauge over a Bourdon tube gauge?

Diaphragm pressure gauges (WIKA series 432.50, for example) are ideal for low-pressure ranges, viscous or crystallizing media, and applications where the process fluid can clog a Bourdon tube. The diaphragm isolates the measuring element with a flexible membrane. I used to think diaphragm gauges were only for gas applications — wrong. They’re actually common in wastewater, chemical feeding, and food processing where you need a flush diaphragm. One thing I’d add: if your process has pulsation or vibration, a diaphragm gauge handles it better than a Bourdon tube because there’s less mechanical linkage.

3. How do I verify the accuracy of a WIKA differential pressure gauge in the field?

Verification usually requires a pressure calibrator and a reference gauge. But here’s a trick: many technicians reach for a multimeter to check the output of a pressure transmitter rather than the gauge itself. If you’re using a Fluke 289 True RMS multimeter, you can measure the 4-20 mA loop from a WIKA pressure transmitter and compare it to the gauge reading. But — and this is critical — the gauge and the transmitter may have different accuracy classes. I’ve seen engineers assume a 0.5% gauge is ‘close enough’ to a 0.1% transmitter. That’s a mistake. For a reliable field check, use a NIST-traceable pressure source and a calibrated reference; the multimeter is just a secondary indicator.

4. What does “True RMS” mean for a multimeter, and does it matter for pressure instrument work?

True RMS (like the Fluke 289) means it measures the actual heating value of AC signals, even if the waveform is distorted. For pure sine waves, any multimeter works. But in industrial environments, VFDs, motor drives, and switching power supplies create non-sinusoidal waveforms. If you’re troubleshooting a pressure transmitter’s power supply or checking an encoder output, a True RMS meter gives you accurate readings. The Klein vs Fluke debate often comes up in this context — both are good, but Fluke’s low-pass filter (on the 289) helps when you’re looking at noisy signals from a pump or a variable frequency drive.

5. How do encoders relate to pressure measurement?

Encoders aren’t pressure instruments themselves, but they’re often used in flow measurement systems that depend on differential pressure. For example, an orifice plate DP cell sends a signal to a controller, which might use an encoder to track valve position. In our audits, we’ve found that encoder selection gets overlooked. A low-resolution encoder can introduce significant uncertainty in flow totalization. I recommend specifying at least 1,000 PPR (pulses per revolution) for DP-based flow applications. WIKA doesn’t make encoders, but when you’re building a measurement chain, the encoder’s accuracy class should match or exceed the DP gauge’s class. Otherwise, you’re wasting money on the precision instrument.

6. Is a Klein multimeter good enough for calibrating a WIKA pressure transmitter?

It depends on what you’re calibrating. For a simple continuity check or voltage test, a Klein MM700 is more than adequate. But for transmitter calibration, you need a meter with at least 0.1% DC accuracy and the ability to source or measure 4-20 mA. The Fluke 289 offers 0.025% basic DC accuracy and a built-in low-pass filter — that’s overkill for a visual check but appropriate for loop validation. Real talk: if you’re only doing go/no-go checks, save the money and use Klein. If you’re documenting calibration for ISO 9001 or a quality audit, invest in the Fluke. I’ve rejected calibration records because the technician used a 0.5% meter on a 0.1% transmitter — that’s a mismatch.

7. What’s the most common mistake when selecting a WIKA diaphragm pressure gauge?

People assume that a larger diameter diaphragm equals better accuracy. Actually, the fill fluid and the material compatibility matter more. For example, a flush diaphragm with a Viton seal handles aggressive chemicals better than a stainless steel diaphragm with a NBR seal — but many specs only list the diaphragm material. I learned this the hard way when a batch of 50 gauges failed after three months in a chlorine environment. The diaphragm was 316L, but the O-ring was Buna-N. The vendor said it was “within industry standard,” but we rejected the batch. Now every contract includes a clause specifying seal material alongside diaphragm material. Lesson: don’t just copy-paste specs from a previous project.

8. How often should I recalibrate a WIKA differential pressure gauge?

The industry standard is every 12 months — but that’s a baseline. In high-vibration or thermal cycling applications, I’ve seen drift happen in 6 months. Conversely, in a clean, stable lab environment, a DP gauge might hold spec for 24 months. WIKA’s documentation recommends an initial recalibration after one year, then adjusting based on actual drift data. I always tell engineers: “Don’t ask how often to calibrate — ask how often you’re willing to risk an undetected error.” For critical safety loops, I’d rather over-calibrate than under-verify. The cost of an extra calibration (~$150 per gauge) is trivial compared to a process upset.

One last thing — if you’re using a Fluke 289 as part of your calibration kit, remember that it needs calibration too. I’ve seen facilities send out their pressure transmitters but overlook the multimeter. By 2025, most quality auditors check that all test equipment has current certification. Don’t be the one who explains why your “calibrated” transmitter was measured with an uncertified meter.