MAMAC Systems, Parts, LONG PartsPros

Product Feature: Mamac Low Pressure Sensor

Differential transducers measure pressure and convert the reading into an electrical signal that can be read by a controller. They are used to measure pressure in variable air systems. To measure differential pressure across a fan for proper operation, or to measure differential pressure across a filter bank to indicate a dirty filter.

In a variable air volume system, the transducer can monitor duct or building/space static pressure to control supply fan speed, exhaust fan speed, or exhaust damper modulation.

To monitor a fan or filter bank, a pitot tube is placed upstream of the fan or filter and attached to the low-pressure port of the transducer. A second pitot tube is placed downstream and attached to the high-pressure port. The transducer will report the differential pressure in the duct across the fan or filter.

The Mamac PR-274/275 low pressure sensor offers multiple pressure range options with up to six field-selectable ranges within each option. The ranges can be bidirectional (ie. -2.5” w.c. to +2.5” w.c.) or unidirectional (ie. 0 to 5.0” w.c.). The advantage to the customer is that a unit can be selected without knowing the exact range needed and then field configured to the desired range.

The unit is available in two output versions, 4-20mA 2-wire or 0-5VDC/0-10VDC.  The 4-20mA unit has built-in reverse polarity protection. The VDC unit is field selectable between 0-5VDC or 0-10VDC by setting a dip switch.

Supply voltage is 12-40VDC for both units. Additionally, the VDC unit supply voltage can be 12-35VAC.

There are two options for install: the PR-274 offers a NEMA 4 enclosure while the PR-275 is a panel-mount device.

We sell the full range of these transducers. If you are not sure about your requirements and need help with the selection, please contact LONG PartsPros and we will help you determine the sensor that best fits your application.


Celeste Duggan

Celeste is an application engineer with LONG’s engineering group in Colorado. She enjoys sailing, cooking, and tinkering with her home automation system.