Making sense of M2M and telemetry
I remember my accountant telling me once when doing some end of year accounts ‘rubbish in, rubbish out’ and the saying came back into my head recently when someone was describing to me an experience they had had with remote monitoring (M2M, telemetry….. you choose the phrase that you think is best).
As the M2M sector gathers momentum we are hearing a lot of talk about chipsets and modules, sim cards and cloud computing but we need to remember my accountant – rubbish in, rubbish out…. A lot of M2M applications involve measurements being taken and transmitted – from water, gas and electricity metering to heart rate monitoring.
The range physical variables that are being measured would take me all day just to type out let alone work out the best way to perform the measurement and develop the technology, but to seems to be the last thing on people’s minds. Perhaps it should be the first..?
Tank Level Monitoring
The telemetry experience I mentioned above related to tank level monitoring and it was a case of misapplication. An absolute pressure transmitter had been used. Yes, pressure = density x gravity x height, so the pressure exerted on the sensor face does change as the height of liquid above it changes, but someone along the line had forgotten that above the tank there’s the atmosphere and the atmospheric pressure changes. You can use a pressure sensor in this application so long as you compensate for the atmospheric changes (usually with the right type of pressure sensor). What is the right technology for level measurement..? You have to consider the budget, the accuracy, the tank size, the product and the conditions. You could use an ultrasonic sensor, one that transmits an ultrasonic pulse and times how long it takes to bounce back from the liquids surface. Ultrasonic level sensors are great and have their place, but how well do they suit an application when they are only powered momentarily once a day..? Could condensation build up on the face of the sensor and effect the measurement..? If this happened would you know about it or would you get a rogue reading, think the tank was empty and send a tanker out to fill..?
Level Monitoring Sensors
Sensors need to be applied correctly or else we, as a sector, are in danger of having great communication solutions that are actually delivering rubbish data.