As remote tank level measurement begins to permeate the industry, the use of batteries is growing rapidly. With batteries comes a new set of requirements for tank level sensors. If they take too long to qualify a measurement, or if they draw too much power, it becomes difficult to find a battery that will last very long.
So you need a power budget. A power budget details exactly how much power your remote monitoring installation will use and when – resulting in solid estimation for when the battery will need to be changed.
To create an accurate power budget, you’ll need some information from your sensor supplier. Here are 3 questions you need answered about your remote tank level monitoring sensor:
This one seems like the most obvious. If you know how much battery juice your sensor will use, then you’ll be able to calculate when the battery will run out, right?
Yes, you can make that calculation, but in order to get your battery to last more than a few months, you need to manage the power consumption by turning everything off when you don’t need a measurement. So the rest of the questions relate to how the power is used during the on and off cycling process.
Truthfully, your sensor will require a controller of some kind to turn the power on and off. Therefore, it’s the controller, not the sensor, that would be using a bit of power in sleep mode – just enough to keep it’s timer running so it can turn on at the appropriate moment.
The sensor itself won’t be using any power during sleep mode. If your sensor supplier is also your controller supplier, or the control function is integral to the sensor, you would ask them about idle current draw.
That said, you’d need to know current draw in both sleep and active modes – regardless of what device is using it up.
Finally, once you know current draw in all modes, you’ll need to know how much time your equipment will spend in those modes. This will change with each sensor, though not always dramatically, as each technology will require a different warm-up, measurement, and transmission time.
For example, a pressure sensor needs only a few milliseconds to start measuring, and a few more to transmit. You’ll have a qualified measurement in a total of about 1 second or less.
An ultrasonic, on the other hand, may require several seconds just to turn on, qualify a measurement, and transmit. A radar sensor takes even longer – some longer than 30 seconds.
While we’re still talking about seconds, this all adds up. Measurement time is a critical part of the power budget equation.
If you haven’t already, there are a few other questions you need to ask before you jump into a battery powered remote tank level monitoring installation. Above, we covered sensor specific questions that you’ll likely get answered from your sensor supplier or manufacturer.
Here are a few more questions that will require a bit more research:
It’s important to choose low power equipment when using batteries to keep cost and hassle down as much as possible. Our PT-500 submersible pressure transducer is a great option for remote tank level measurement as it has a very low current draw and can produce a measurement in about a second.
Let us know if you have questions about our sensors to help you build your power budget. We have a few sensors that are very well suited for batteries and remote installations.
top photo credit: Andy Rennie via flickr cc cropped
