Pressure Gauge Selection: Dial Size, Range, Glycerin Filling and Stainless Steel
Bourdon tube, capsule and diaphragm pressure gauges: which series for which pressure and medium?
Six Questions in Pressure Gauge Selection
A pressure gauge indicates pressure locally with a mechanical pointer and requires no electrical power or controller. The right series is identified with six questions:
- Is the medium corrosive? If not, S100 or H200; if corrosive, all-stainless A300.
- Is the line subject to vibration? Glycerin-filled (H200G, A300G) on pump and compressor lines; dry model at high temperatures.
- Which pressure range? Sized so steady operating pressure does not exceed 3/4 of full scale; C600 for mbar ranges.
- Which accuracy class? Cl.2.5, Cl.1.6 or Cl.1.0 (2.5%, 1.6% or 1% of full scale).
- Which dial size and connection? Ø40–160 mm; G1/8, G1/4B or G1/2B; bottom, back, panel or flanged mount.
- Hygienic or viscous fluid? Flush-diaphragm A300.TC1.
Aterma Pressure Gauge Series
Values are taken from Aterma datasheets; all are manufactured in accordance with EN 837 (C600: EN 837-3).
| Series | Dial size | Pressure range | Accuracy | Ambient / fluid temperature | Protection | Materials | Application |
|---|---|---|---|---|---|---|---|
| S100 standard | 40 · 50 · 63 · 100 · 160 mm | Ø40: -1…0 to 0…160 bar Ø50: 0…315 Ø63: 0…400 Ø100: 0…600 Ø160: -1…0 to 0…60 bar | Cl.2.5 (Ø160: Cl.1.6) | -20…+60 °C / max +60 °C | IP41 | Painted steel case, copper alloy Bourdon tube, brass connection | Non-corrosive gas and liquid: pneumatics, HVAC, marine, medical |
| H200 / H200G industrial | 100 · 160 mm | 0…0.6 to 0…600 bar; -1…0 to -1…+24 bar | Cl.1.0 | H200: -40…+60 / max +80 °C H200G: -20…+60 / max +60 °C | H200 IP54; H200G IP65 | 304 stainless case and movement, copper alloy Bourdon tube, brass connection G1/2B | Non-corrosive, particle-free gas and liquid: machinery, power plant, process, marine |
| A300 / A300G all-stainless | 63 · 100 · 160 mm | Ø63: 0…1 to 0…1000 bar Ø100 and Ø160: 0…0.6 to 0…1600 bar; -1…0 to -1…+24 bar | Ø63: Cl.1.6 Ø100/160: Cl.1.0 | A300: -40…+60 / max +200 °C A300G: -20…+60 / max +100 °C | IP65 | 304 case, 316L Bourdon tube and connection (G1/4B Ø63; G1/2B Ø100-160); optional Monel | Corrosive and aggressive environments: chemical, petrochemical, food & beverage, natural gas, marine |
| A300.TC1 / A300G.TC1 flush diaphragm | 63 · 100 · 160 mm | -1…0 bar to 0…40 bar (depending on clamp size; max 0…16 bar for DN50 and 2 inch) | Ø63: Cl.1.6 Ø100/160: Cl.1.0 | A300: -20…+40 / max +100 °C A300G: -25…+40 / max +100 °C | IP65 | 316L diaphragm, 316 diaphragm body (optional 316L); DN25–DN50 (DIN 32676) or 1–2 inch (ISO 2852) | Food, dairy, pharmaceutical, chemical and biochemical, high-viscosity fluids |
| C600 capsule diaphragm | 63 · 100 · 160 mm | 0…40 to 0…600 mbar; -40…0 to -600…0 mbar | Positive Cl.1.6; vacuum Cl.2.5 | -20…+60 °C / max +60 °C | Ø63 IP32; Ø100/160 IP54 | Copper alloy capsule and movement, brass connection | Natural gas, low pressure, vacuum, medical, laboratory |
Available on request across all series: calibration certificate, custom dial design, alternative pressure scales (kg/cm², psi, MPa, etc.); and on S100/H200/A300, alternative process connections (such as 1/2 NPT). Maximum pointer (H200.SP) and Monel Bourdon options are also listed in the H200 and A300 datasheets.
Checklist for the Right Pressure Gauge
Range and operating pressure
Aterma specifies continuous steady operating pressure as 3/4 of full scale. Place normal operating pressure between the lower half and 3/4 of the scale; for short-term overpressure, 1.25 times full scale is permitted up to 100 bar on H200, and 1.10 times between 600 and 1600 bar on A300.
Accuracy class
The class number represents the permissible error as a percentage of full scale: 0.1 bar for Cl.1.0 and 0.25 bar for Cl.2.5 on a 0–10 bar gauge. As ambient temperature deviates from the 20 °C reference, an additional error of 0.04% of full scale per degree is added (0.06% on C600).
Dry or glycerin-filled?
Choose glycerin-filled when vibration, pulsation or pointer oscillation is present. Choose dry when fluid temperature is high: A300 handles fluid up to +200 °C, A300G up to +100 °C, H200 up to +80 °C and H200G up to +60 °C. Glycerin-filled models are rated IP65.
Connection and mounting
Standard connections are G1/8 (Ø40), G1/4B (Ø50–63) and G1/2B (Ø100–160), available in bottom, back, panel-mount or front-flange styles. Dial size and thread size are selected together; alternative process threads such as 1/4 NPT or 1/2 NPT are supplied on request.
Bar, MPa, kPa, psi and kg/cm²
Aterma pressure gauges can be ordered with kg/cm², psi or MPa scales on request; conversions follow standard physical constants.
| 1 bar | MPa | kPa | psi | kg/cm² |
|---|---|---|---|---|
| 1 bar | 0.1 | 100 | 14.50 | 1.0197 |
| 10 bar | 1 | 1000 | 145.0 | 10.197 |
Related pages: Aterma pressure gauges, transmitters and bimetal thermometers · flow sensor selection
Frequently Asked Questions on Pressure Gauge Selection
Glycerin-filled vs dry pressure gauges, dial diameter, accuracy class, stainless steel and diaphragm seal options.
When is a glycerin-filled pressure gauge used?
On pump, compressor and vibrating lines, the pointer flutters and becomes unreadable; glycerin filling dampens the pointer and extends the service life of the movement. In the Aterma range, H200G and A300G are the glycerin-filled versions. Temperature limits of glycerin-filled models are lower than those of dry models: process medium max +60 °C for H200G and max +100 °C for A300G.
What is the difference between a dry pressure gauge and a glycerin-filled gauge?
A dry gauge is sufficient on vibration-free, static pressure lines and operates across a wider temperature range: process medium max +80 °C for H200 and max +200 °C for A300. In a glycerin-filled model, the pointer is dampened and ingress protection increases to IP65 (H200 dry is IP54). Select glycerin-filled when vibration is present, and dry for high process temperatures.
How is the dial size (Ø63, Ø100, Ø160) selected?
Dial diameter determines viewing distance and scale resolution. Aterma S100 is available in 40, 50, 63, 100 and 160 mm; H200 in 100 and 160 mm; and A300 in 63, 100 and 160 mm. As diameter increases, the available pressure range and accuracy class also change: in S100, Ø160 mm is Cl.1.6 and the other sizes are Cl.2.5; in A300, Ø63 is Cl.1.6 while Ø100 and Ø160 are Cl.1.0.
What do accuracy classes Cl.1.0, Cl.1.6 and Cl.2.5 mean?
The class number is the permissible error limit expressed as a percentage of full scale: Cl.1.0 is 1% of full scale and Cl.2.5 is 2.5%. On a 0–10 bar Cl.1.0 pressure gauge, the error limit is 0.1 bar; on a Cl.2.5 gauge, it is 0.25 bar. According to Aterma datasheets, an additional temperature error of 0.04% of full scale per degree is added as ambient temperature deviates from 20 °C.
What fraction of full scale should the operating pressure be?
Aterma datasheets specify continuous steady operating pressure as 3/4 of full scale. For short-term overpressure, the limit is full scale for S100; 1.25 times full scale up to 100 bar and 1.15 times between 100 and 600 bar for H200; and 1.10 times between 600 and 1600 bar for A300. Where pressure spikes or pulsations exist, select a wider scale range or a glycerin-filled model.
Is a stainless steel case gauge the same as an all-stainless pressure gauge?
No. On the H200, the case, movement and bezel ring are 304 stainless steel, but the Bourdon tube is copper alloy and the process connection is brass; it is suited for non-corrosive gases and liquids, not corrosive media. On the A300, the Bourdon tube and process connection are also 316L stainless steel (optional Monel); select this series for corrosive and aggressive media.
When is a diaphragm seal pressure gauge required?
When the fluid is highly viscous, sticky, crystallizing or requires hygienic design. Aterma A300.TC1 and A300G.TC1 feature a 316L flush diaphragm, easy disassembly, and DN25–DN50 (DIN 32676) or 1–2 inch (ISO 2852) clamp connections; maximum working pressure is 40 bar and maximum fluid temperature is +100 °C. They are used in food, beverage, dairy, pharmaceutical and biochemical lines.
Which pressure gauge measures very low pressure (mbar)?
The Aterma C600 capsule diaphragm pressure gauge (EN 837-3) covers 0–40 mbar to 0–600 mbar positive pressure and -40…0 to -600…0 mbar vacuum. It is specified for natural gas pressure measurement, vacuum systems, medical and laboratory applications. Accuracy is Cl.1.6 on positive scales and Cl.2.5 on vacuum scales.
When is a pressure transmitter needed instead of a pressure gauge?
A pressure gauge indicates pressure locally with a mechanical pointer; if PLC, SCADA or alarm integration is required, a transmitter with a 4-20 mA output is needed. See Aterma pressure transmitters and gauges for options.
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