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SA Instrumentation & Control Buyers' Guide

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Battery-operated pressure measurement
July 2009, Pressure Measurement & Control

Why would anybody want to measure pressure in a remote location where typically no power is available? What would such a measurement be used for (realtime applications or data-logging)? What would be the requirements of a pressure sensor to be used in such an application? These are some of the application-related questions that come to mind.


Current loop (4-20 mA) and fieldbus type measuring instrumentation consumes too much power to be used in battery driven applications. For that matter, even the use of a built-in microprocessor in the pressure device for scaling and calibration purposes might cause the instrument to consume too much power.

In many instances, like data-logging, the data will be stored at a given dead band and interval in memory until collected for analysis. Some applications might require action on the measurement in which case the measurement will be passed on to a second, or integrated, battery-driven instrument that can act on the measurement – like an RF transmitter or cellular device.


Let us look at the typical requirements for this measurement to make it useful in such an application:

* The instrument must be driven from a battery (typically between 8 and 12 V), and the output must be a high impedance voltage. Usually the load current on the output must be less than 1 mA at 5 V, which gives a power consumption of less than 5 mW. Most commercial transducers will not come close to that value.

* If the output of the sensor is in the mV range it makes field measurement for calibration more difficult.

* Typical battery-operated flowmeters can work for five years from the same battery. For a pressure measurement device to operate for a similar period it would need a 50 Ah battery for the specified requirements.

* Ingress protection requirements determine whether the sensor has to be housed in an additional enclosure or whether it can be, for instance, submerged.


The cost of pressure transducers varies a lot according to the amount of stainless steel used, the sophistication of the electronic circuitry, the ingress protection requirements, temperature compensation, etc. The manufacturing technology used will also influence the cost, not to speak of additional requirements for a battery driven device. Bonded foil strain gauge (BGSG) transducers have been around for some 60 years, and is a well proven technology. The downside to a BFSG sensor is that it is labour intensive to manufacture due to component matching on the strain gauges. The advantage is that it is more or less a mechanical device, and as such it is easy to design-in over pressure stops that can prevent the instrument from being damaged in the event of a pressure spike. The device electronics is often discrete components, which make it easily adaptable to different output requirements, as in this case for a battery-driven low power device with less than 1% accuracy. These devices can also be used at extreme temperatures from -40 to +120°C.

Typical application

Typical applications can include tyre pressure monitoring, portable blood pressure measurement and water-line pressure monitoring. Each has its own unique set of requirements.

In the water industry (commercial and residential distribution) a device commonly used is a flowmeter. Traditionally these flowmeters are mechanical such as those located at most residential premises and in many cases in the main distribution lines between utilities and reservoirs. Newer types of flowmetering used are battery-driven magnetic and ultrasonic flowmeters. An important requirement for these meters is that they have to be certified for custody transfer (billing purposes). Most open channel flowmetering uses a level measurement and some like at a weir will use a pressure instrument for flow measurement.

Just as in the electrical world where current and voltage together are used to calculate power, measuring both flow and pressure gives a measure of the power required to pump the water. Simplistically stated for electricity the apparent power is S = V*I where V is the voltage and I the current, the power required to pump water is P = p*V where p is the pressure and V is the volumetric flow rate.

In the case of a furnace, measuring only the current and not the voltage would not give a clear idea of the power consumption. In a pumped water application, not having the pressure would be like not having the voltage, and trying to answer the question: why is no water flowing?

Important operational requirements for the water industry like water balancing, leak detection, disaster aversion, demand management, pump station scheduling etc, are all influenced by measurements that have to be taken at locations, where mostly no power supply exists. In South Africa problems like distances between pipe lines, theft of cables and solar panels has forced us to apply old technologies in new ways to overcome these challenges.

At SCE we have been involved in the design of such applications for major water utilities in South Africa, and we have proven technologies for many applications.

For more information contact Jaco Hoogenboezem, Supervisory & Control Expertise SA, +27 (0)83 282 5706,,

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Further reading:

  • Hygienic diaphragm pressure gauges
    December 2018, WIKA Instruments, Pressure Measurement & Control
    WIKA has expanded the application range of its hygienic diaphragm pressure gauges with the model PG43SA-S, which is now also available in a version with ATEX approval. The pressure gauge can thus be used ...
  • Analysing pressure peaks
    November 2018, Instrotech, Pressure Measurement & Control
    Keller’s Leo 5 high-resolution digital manometer features precise sensor technology, fast signal processing, peak recording and data storage with a time stamp. Designed for deployment in hostile environments, ...
  • Pressure measurement with dual display
    October 2018, Pressure Measurement & Control
    The PSQ series dual digital display pressure sensors from Autonics allow users to monitor both PV and SV readings. The 12-segment LCD display is capable of displaying various alphanumeric characters for ...
  • Flush-mount pressure transmitter
    October 2018, ASSTech Process Electronics + Instrumentation, Pressure Measurement & Control
    Specifically developed for the supervision of clean rooms, the Kimo CPE 300 transmitter is dedicated to the measurement of low pressure or depression of air or neutral gasses from 0/10 Pa to -1000/ 1000 ...
  • Innovative compact orifice plate
    October 2018, WIKA Instruments, Pressure Measurement & Control
    Compact orifice plates can be used without difficulty for the measurement of liquids, gases and vapours. WIKA’s new compact orifice plate Model FLC-CO enables direct mounting of differential transmitters. Differential ...
  • Selecting appropriate pressure gauges
    September 2018, SA Gauge, Pressure Measurement & Control
    The use of pressure transmitters as the primary source of pressure measurement in sophisticated process applications is very popular. However, as a backup to the electrical readings, and as a local display, ...
  • Keller sensors for static and ­dynamic pressures
    September 2018, Instrotech, Pressure Measurement & Control
    Keller’s M5 series, the sensor for static and highly dynamic measurements (up to 50 kHz), represents something unique when considering the operating temperature range (up to 180°C), measurement accuracy ...
  • Pressure transmitters SIL certified
    August 2018, ASSTech Process Electronics + Instrumentation, Pressure Measurement & Control
    Safety Integrity Level (SIL) is gaining increasing importance in the process industry. Jumo offers a comprehensive product portfolio in this arena with recent additions being the pressure transmitters ...
  • Emerson expands its pressure gauge portfolio
    July 2018, Emerson Automation Solutions, Pressure Measurement & Control
    Emerson has introduced the Rosemount Smart Pressure Gauge to help users gain better visibility of field changes. It utilises industry-proven Rosemount pressure sensor technology to deliver reliable pressure ...
  • Air velocity and flow measurement in system ducts
    July 2018, ASSTech Process Electronics + Instrumentation, Pressure Measurement & Control
    Kimo manufactures a new system to measure air velocity and airflow in ducts. The Debimo measuring blades can easily be installed inside any circular or rectangular duct and the streamlined design avoids ...
  • Precision pressure calibrators
    July 2018, Comtest, Pressure Measurement & Control
    Fluke’s 721 precision pressure calibrator has dual isolated sensors for gas custody transfer applications for pressure calibration and temperature measurement. This allows for simultaneous static and ...
  • Heavy-duty pressure switch
    July 2018, WIKA Instruments, Pressure Measurement & Control
    From pumps through hydraulic systems to autoclaves, WIKA’s new model PSM-550 heavy-duty pressure switch has been designed for superior industrial applications. The new instrument switches electrical ...

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