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Pressure capsules, pressure measuring cells and diaphragms, also called pressure measuring elements, convert pressure into travel. This stroke drives the pointer mechanism of a pressure gauge, adjusts a pressure regulator or is picked up by a sensor.
octogon manufactures these elements as a standard range in many sizes and to your specifications, in highly resistant materials and, on request, with fittings, nipples or base plates. We guarantee linearity errors below 1 % of full scale, and lower on request.
The range: capsules, diaphragms, assemblies
Eight products in three groups are listed in the shop with dimensions and datasheet. If none of them fits, we manufacture to your drawing or sample.
How a pressure capsule works
A diaphragm is a pressure-to-stroke converter: pressure on one side deflects it, and the corrugation makes the travel large and even. Two diaphragms joined at the rim form a capsule, also known as a capsule spring or pressure cell.
The measuring pressure enters the capsule through the connection. Its height changes with the difference between internal and external pressure. If the same pressure acts on both sides, the deflection stays at zero. If one capsule does not give enough stroke, several are joined into a capsule stack.
Designs and what they are used for
Absolute pressure capsules
Evacuated, hermetically sealed capsules for aneroid barometers and altimeters. The spring force of the diaphragms and the external air pressure are in balance; when the air pressure changes, the capsule height changes, and a pointer mechanism transfers this to the display.
We supply absolute pressure capsules and capsule stacks in various diameters and strokes, with silver coating on request. For weather stations we also make temperature-compensated capsule stacks.
Differential and relative pressure capsules
They measure the pressure outside the capsule relative to the internal pressure. Two joined diaphragms allow larger strokes, and the measuring pressure is fed in through a pressure connection.
We make them from CuBe2, 1.4435 and 1.4571 in various diameters; other materials, diameters and custom connections on request. Standard range: pressure capsules KEOA, KKOA and KDOA.
Diaphragms, plate springs, disc springs
They are used where very hot or highly corrosive processes do not allow the instrument to be connected directly to the medium. As an isolating diaphragm they transmit the pressure between medium and sensing element; as a plate spring they are the measuring element of a pressure gauge themselves.
Diaphragm systems
Complete systems for measuring micro-pressure and vacuum in gases, including applications with high demands on corrosion resistance. We develop them from scratch or from your drawing or an existing sample, and adapt them to the pressure and accuracy range, including vacuum and vacuum-to-pressure.
Ready-to-fit assemblies: KBOA, KMOA and KUOA.
Linearity or stroke: what the design targets
Every element is designed for what your application needs. The two goals partly exclude each other, so we settle them at the start.
For linearity
For pressure gauges, pressure transmitters and blood pressure monitors. We guarantee linearity errors below 1 % of full scale, and lower on request.
For stroke
For pressure regulators, pressure surge dampers and pressure indicators, where linearity is not required but the largest possible travel is.
With many materials, hysteresis is practically not measurable.
The standard range at a glance
The full-scale values are set per size within the stated span. Accuracy classes of the capsules and of the plate-spring measuring diaphragm: 1 · 1.6 · 2.5 %.
| Product | Type | Diameter | Measuring range | Stroke | Material | Connection |
|---|---|---|---|---|---|---|
| KEOA | Pressure capsule | Ø 48 … 114 mm, 6 sizes | 0 … 0.2 to 0 … 100 kPa | 1.1 … 1.5 mm | 316L | M5 or custom |
| KKOA | Pressure capsule | Ø 38 … 114 mm, 8 sizes | 0 … 0.2 to 0 … 100 kPa | 1.1 … 1.5 mm | CuBe (Ø 38), bronze | M5 or custom |
| KDOA | Pressure capsule, double diaphragm | Ø 38 … 114 mm, 8 sizes | 0 … 0.2 to 0 … 100 kPa | 2.2 … 3 mm | CuBe (Ø 38), bronze or 316L | M5 or custom |
| KPOA | Plate-spring measuring diaphragm | Ø 75, 100, 130 mm | 0 … 1 to 0 … 2500 kPa | 1.1 … 1.3 mm | 316L, tantalum, Hastelloy, titanium and others | M3.5 |
| KIOA | Isolating diaphragm | Ø 12.4 … 110 mm, 26 models | – | – | 316L, tantalum, HC276, HB, Monel, titanium, nickel | – (thickness 0.025 … 0.1 mm) |
| KBOA | Diaphragm box assembly | Ø 56.5 and 72 mm | 0 … 1 to 0 … 100 kPa | – | Stainless steel | M5 custom |
| KMOA | Diaphragm box assembly, monolithic | Ø 45, 56.5 and 72 mm | 0 … 1 to 0 … 160 kPa | – | – | M5 custom |
| KUOA | Single-piece diaphragm assembly, overpressure | Ø 45, 56.5 and 72 mm | 0 … 1 to 0 … 160 kPa | – | – | M10 × 1 |
All dimensions per size are in the datasheet on the respective product page.
Materials
We make metal diaphragms in diameters from 10 to 137 mm, among others from these materials. Which one fits depends on the medium, the temperature and the required stroke.
Applications
- Pressure gauges and diaphragm pressure gauges
- Pressure transmitters and pressure sensors
- Diaphragm seals with isolating diaphragm
- Blood pressure monitors
- Aneroid barometers, altimeters and weather stations
- Pressure regulators, pressure surge dampers and pressure indicators
- Micro-pressure and vacuum measurement in gases
What we need for a quotation
- The measuring task: absolute, differential or gauge pressure, measuring range and overload
- The goal: good linearity or the largest possible stroke, and how much stroke you need
- The medium: gas or liquid, temperature, corrosive components
- The installation space: diameter and height
- Material and connection: preferred material, thread, nipple or base plate
- Quantity and required date
A drawing, a sample or the product code from the standard range is enough for a first assessment. If something is missing, send what you have and we will clarify the rest together.
Describe your application using the quotation form.