I have a pretty stupid question that I can't figure out. I have a setup in which I use a Particle Electron to power two JSN-SR04T ultrasonic sensors. See below:
The setup works fine, and I'm interested to test how much current the sensors draw from the LiPo. I understand to measure current I'm required to put it in series - however, I'm not receiving any meaningful readings from both my multimeters (Innova 3320 and DT830B), probably because I'm using them wrong.
To power the sensors, two jumper wires run from the Electron's 3V3 pin to the sensor's 5V pins (the sensor can be powered by 3.3-5.0V). The loop is completed with two jumper wires from the sensor's GND pin to the Electron's GND. How would I go about measuring the current correctly here?
I'm expecting 10-20mA per sensor.
The ammeter goes in series with the current path through the load. Either on the high or the low side. So between the 3.3V pin of your Electron and the 5V pin of your sensor, or between the GND pins of the sensor and the Electron. So really in place of any of the jumper wires you mention in your post.
Assuming that you are using the multimeter correctly, it could be that your sensors draw only very little current, and/or in short bursts.
Try it on something that draws predictable current, like a 330R resistor, see if you measure 10mA.
Hello Vitesze,
Disconnect the battery (+) lead to open the
circuit. Set your meter to read 100 mA DC.
Remove the jumper and connect the meter
(-) lead to the battery (-) and the meter (+mA)
lead the sensor (-). [The meter is now in the
current path.] Switch the meter ON and
reconnect the battery (+) lead. You should be
reading the sensor current.
Herb
Jobi-Wan:
The ammeter goes in series with the current path through the load. Either on the high or the low side. So between the 3.3V pin of your Electron and the 5V pin of your sensor, or between the GND pins of the sensor and the Electron. So really in place of any of the jumper wires you mention in your post.
Assuming that you are using the multimeter correctly, it could be that your sensors draw only very little current, and/or in short bursts.
Try it on something that draws predictable current, like a 330R resistor, see if you measure 10mA.
Ah, I must've blown the fuses in my multimeter previously due to improper use. I'm never able to measure any current, and when I opened the case it did look like the connector in the fuse was disrupted.
As you have two meters measure he fuse continuity of the fuse with the other meter.
In fact most meters will measure continuity with no fuse in so you could use the same meter if you removed the fuse.
Be sure to use the same fuse rating as the existing fuse so the electronics are not damaged in future mistakes.
Also not that a lot of meters these days have a separate input for current measurements, remember to change the leads over if yours is of this type.