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Electronic pressure sensor with ‘analogue’ display

28 May 2009

“Pressure gauges with a moving needle may conjure up thoughts of old-fashioned engineering, but maybe there’s a place for such things yet,” says Michael Schimanowski, the ifm electronic product manager for a new series of pressure measurement instruments.

Ifm electronic's PG Manometer
Ifm electronic's PG Manometer

The people at ifm call it a “fusion of modern technology with classic functionality,” this modified PI series of pressure sensors attached to a 100mm dial display.

“Add a modern sensing element and some state-of-the art electronics, and there you have it: the new PG Manometer range,” says Mr. Schimanowski, sitting in the bar/restaurant in the middle of ifm electronic’s huge stand at Hannover Fair.

To demonstrate the pressure gauge, the company had a half dozen custom transparent plastic stands made to hold the instrument. By pressing on a plunger the ifm personnel could pump up the air pressure to show how the instrument operates.

But that is no ordinary gauge display, like on your grandfather’s manometer. It has a small stepper motor driving the needle, as in a car’s speedometer, and a ring of 114 LEDs, one for each tick mark on the dial.

These are used to illuminate various set and reset points, selectable with the two optical buttons at the bottom.

There are also a lot of other things that can be selected on the dial, such as range, hysteresis, damping, display units, and electronic locking of the settings.

A real curiosity on the dial is the needle when it’s moving: five LEDs ‘follow’ it so the observer can tell at a glance if it is moving in the direction of up or down (see lower photo).

Michael Schimanowski
Michael Schimanowski

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Michael Schimanowski pumps up one of the

transparent plastic demonstrator units to show

how the pressure gauge works.

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So, it is one device instead of two: “No longer does the user need to have a separate pressure gauge and a pressure switch,” says Mr. Schimanowski, “because of course the PG Manometer is more than just a visual indicator, though it does that with a digital LED display as well as the pointer. It is also a versatile pressure sensor, with an output capable of switching 250 mA.”

The output is selectable, normally open or normally closed, and able to automatically detect PNP or NPN. The second output is a scalable analogue current signal.

Since it is entirely electronic, it does have one problem mechanical pressure gauges don’t have—it won’t function without power.

PG Manometer with LEDs in dial
PG Manometer with LEDs in dial

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Notice how the five LEDs "following" the

pointer give an instant indication to the

observer that it is increasing.

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The mounting position does not pose any problems, as the display can be rotated through 350 degrees.

Versions so far available cover eight different ranges of relative pressure, starting at –1 bar and extending up to 25 bar. The medium can be liquid or gaseous.

Mr. Schimanowski says food and pharmaceutical applications suggest themselves as ideal for the PG manometer, as the materials used are ideal for those industries, as are the hygienic process connections and seals on offer. Materials in contact with the medium are only high-grade stainless steel, ceramic and PTFE.

But, electronics give it many other advantages, such as the high precision (0.2%). Mr. Schimanowski says it’s far more vibration and shock resistant than standard manometers, and with a list price of under €400 may even be cheaper than similar size mechanical pressure sensors equipped with vibration resistance and hygienic finish options. And the high-purity ceramic measuring cell give it long term stability and good overload protection.


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