How often does a ring-balance gauge need to be readjusted or recalibrated?

No readjustment is required within the specified operating conditions. The measuring principle is based on a fixed calibration weight and unchanging geometry — there is no ageing component in the measurement path. Calibration histories typically show no deviations, enabling significantly extended calibration intervals.

How much does an electronic differential pressure sensor drift over the years?

Diaphragm-based differential pressure sensors have documented drift rates of typically 0.3–1 % per year. For a cleanroom pressure cascade of 15 Pa, that adds up to 2–7 Pa of deviation by the fifth year of operation — half the monitored pressure differential. The ring balance has no ageing component in the measurement path; drift-induced readjustment is not required.

Can a ring-balance gauge be used with aggressive media such as flue gas or biogas?

Yes. The sealing liquid barrier of the ring balance is resistant to aggressive media such as flue gas, biogas and acid vapours — media that attack diaphragm sensors over months. The ring balance is therefore particularly suitable for chemically demanding environments.

Is the ring-balance gauge ATEX-certified for use in hazardous areas?

Yes. The RW65_EX_II is developed as a fully certified intrinsically safe Ex ia device for Zone 0 and is therefore suitable for use in potentially explosive atmospheres under the ATEX directive.

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Knowledge / Measurement principles compared

Ring balance vs. electronic sensors — why the measuring principle matters for low-pressure measurement

Q: Why do manufacturers of electronic transmitters often guarantee only one year of stability for minimum ranges?

Transmitters for ranges such as 40 or 100 Pa generally contain sensors designed for much larger ranges (typically 750 to 2,500 Pa upper range limit), whose signal is electronically amplified onto the small measuring range — known as turndown. Since accuracy and stability figures refer to the sensor's upper range limit, these errors multiply relative to the configured range; the stability guarantee accordingly often shrinks from ten years to one. The ring balance measures 40 Pa natively — calibration weight and measuring element are designed for exactly this range.

For long-term monitoring of small differential pressures below 2 kPa, there is one measuring principle that is structurally unbeatable — and three that require regular intervention. The difference is not price, it is physics: electronic sensors age. The ring balance does not.

The four principles compared

Property	Ring balance	Diaphragm (strain gauge)	Capacitive	Piezoresistive
Measurement path	mechanical (torque)	electrical (strain)	electrical (capacitance)	electrical (resistance)
Drift over 10 years	physically zero	0.2–1 % p.a.	0.1–0.5 % p.a.	0.3–1 % p.a.
Readjustment	not required (within specified operating conditions)	every 12–24 months	every 12–24 months	every 6–12 months
Minimum span	40 Pa	100 Pa	50 Pa	250 Pa
Maximum span	1,800 Pa	several bar	several bar	hundreds of bar
Aggressive media	very good	medium	good	poor
Response / signal quality	span-dependent — low-pass damping at small spans, fast at large spans	ms — software damping in controller typically required	ms — post-filtering required	ms — post-filtering required
On-site display	analog 150×150 mm (standard) or digital LCD	digital, separate	digital	digital
Power supply	transmitter only (optional)	always	always	always
Service life	30+ years documented	5–10 years	5–10 years	5–10 years
ATEX capable	yes (intrinsically safe Ex ia)	yes	yes	yes

Structural strengths of the ring balance

No drift, no readjustment: the measuring principle is based on a fixed weight and unchanging geometry — there is no ageing component in the measurement path. Calibration histories typically show no deviations, enabling significantly extended intervals.
Reliable with aggressive media: flue gas, biogas, acid vapours — everything that attacks diaphragms over months leaves the ring balance's sealing liquid barrier unaffected.
Resolution advantage below 100 Pa: in the sub-100 Pa range — typical for cleanroom pressure cascades and GMP requirements — electronic sensors operate at their resolution limit. The ring balance has a physical advantage here.
Stable signal without software filtering (at small spans): below ~200 Pa span — typical for cleanroom, GMP, and filter monitoring — the sealing liquid acts as a mechanical low-pass filter. Pressure spikes and turbulence are physically damped, keeping the reading steady. At larger spans the calibration weight increases, the restoring force grows, and response time shortens accordingly. Electronic sensors require software filtering regardless of span.
Permanent on-site visibility: depending on the variant, either a 150×150 mm analog scale (readable from two metres, no power needed) or a digital LCD — the measuring element always displays directly, no separate display module required.
ATEX Zone 0 intrinsically safe: the RW65_EX_II is developed as a fully certified Ex ia device — structurally simpler and legally safer than combined solutions.

Technical operating limits

Above 1,800 Pa span: the ring balance is designed for low-pressure differential measurement. For higher pressures, diaphragm sensor technology is the appropriate choice — this is outside our product range.
Dynamic pressure spikes below 100 ms: for pulsation or flow measurement requiring millisecond resolution, piezo sensor technology is required. For static room pressure monitoring and filter supervision, the ring balance response time is fully adequate.

Praxis

The "maintenance-free alternative" argument — and our response

Some manufacturers position their electronic diaphragm sensors as a "maintenance-free alternative to the ring balance." This refers to the elimination of sealing fluid — a valid simplification. However, the decisive question is different: how long does the calibration stay stable?

Diaphragm-based differential pressure sensors have documented drift rates of typically 0.3–1 % per year. For a 15 Pa pressure cascade, that means a deviation of 2–7 Pa by the fifth year of operation — half the monitored pressure differential itself. The ring balance measures purely mechanically: no ageing component in the measurement path, physically zero drift, no drift-induced readjustment.

With minimum spans, a second effect comes into play: electronic transmitters for ranges such as 40 or 100 Pa generally contain sensors designed for much larger ranges (typically 750 to 2,500 Pa upper range limit), whose signal is electronically amplified onto the small measuring range — referred to in data sheets as “turndown”, e.g. 100:1. Since accuracy, temperature and stability figures refer to the sensor's upper range limit, these errors multiply relative to the configured range; for such minimum ranges, manufacturers moreover often guarantee long-term stability for only one year instead of ten. The ring balance measures 40 Pa natively — calibration weight and measuring element are designed for exactly this range.

For applications with long service intervals, regulated calibration requirements or aggressive media — cleanroom, GMP, pharma, biogas, furnace engineering — the ring balance is structurally the superior solution.

Is the ring balance right for your application?

How often should the device be readjusted or recalibrated?

As rarely as possible — plant runs continuously → Ring balance — no readjustment required
Calibration required by regulation (GMP, ISO 14644) → Ring balance — drift-free, calibration history typically shows no deviations → intervals significantly extendable

Which medium is being measured?

Flue gas, biogas, acid vapours, contaminated air → Ring balance — resistant to aggressive media
Clean air, nitrogen, neutral gases → Ring balance — also suitable

What pressure span is required?

Under 100 Pa → Ring balance — clear resolution advantage
100 Pa to 1,800 Pa → Ring balance — full operating range
Above 1,800 Pa → Outside our range — contact us

Frequently asked questions

Your application

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Note: The content of this page is provided for general guidance and replaces neither the operator's risk assessment nor case-by-case verification by qualified personnel. Responsibility for sizing, equipment selection, installation and operation lies solely with the operator. Despite careful preparation, we accept no liability for accuracy or completeness; the currently valid edition of the applicable regulations and standards prevails.