Hey there all,
So I'm currently working on a project that needs to determine dB readings remotely. I have this as the current sound level meter that we are using but I need a way to communicate the data in real time back to an operator on a Nextion display.
There is also force readings and temperature readings being sent back but those were pretty straightforward to read and send using the Arduino. Normally you let the meter run and then you can export the data to a PC and I had originally thought I was going to have to try and map this output to determine what was responsible for listing the peak value.
Fortunately the meter also has an analog output and states that it produces 40 mV/dB. So I was wondering if something like using an AD623AN amplifier to increase that signal to something that the Arduino could process and have it simply connect to an analog input and then send the data to the display the same way we have done for the other sensors.
I'm just wondering if that seems like the best way to go about it and if so what kind of connection I need to go from the 3.5 mm jack on the sound meter to the Arduino input.
Generally the pressure transducers and such that we use would have a scale of 0-40 mV and so a gain of 100 would produce a signal that was easily usable by the Arduino but if this is 40 mV/dB and has an 50 dB span then I assume that means it would produce a range of 0-2000 mV so does that even realistically require the use of an amplifier?
There's also the issue that the meter has variable scales, ideally it will always be used at the highest scale (measuring 80-130 dB) so I'll have to determine if the meter starts at 0 mV for whatever the minimum of the current scale is at or if it stays consistent with the 40 mV/dB.
When I bring up the data sheet for a PCE-322A sound meter I get the following data sheet:
On page 13 of the data sheet I read:
"AC: Output voltage: 1Vrms corresponding to each range
step.
Output impedance: 100Ω
DC: Output voltage: 10mV/dB
Output impedance: 1kΩ "
So you have a DC and AC output and the DC out is 10 mV / db. The full range is 30dB~130dB over 3 ranges. So the maximum DC out I read as 130 * .010 = 1.3 VDC. Since the Arduino is measuring other analog inputs I will guess that the ADC Vref can't be changed to 1.3 volts.
You don't mention what sort of audio you will be listening to? Just for example something like average noise on a factory floor or average noise of traffic in the city? I ask because while those two are easy to measure and record a sharp sound like a gun shot from start to finish is over in about 1.5 mSec and an Arduino is not quite that fast on the analog sampling rate, pretty close but I would not use one.
Yes, the AD623an should work out fine choose the gain to work well with your expected measurement range.
Ron
Yes, unfortunately the ADC Vref can't be changed due to the other systems being read by the arduino.
Thanks for catching my mistake with the output voltage, I was still using the specs from the previous sound meter that we were going to use.
The system is only going to be operated in the 80-130 dB range so if I'm understanding the data sheet correctly the AC output voltage would show different values of Vrms depending on the range and the DC output voltage would always show 10mV/dB starting at 0 mV? So a 0-500 mV full range is what I'd be expecting and so a gain of 10 on the AD623an would then give the 0-5V range.
The sound we're measuring is heavy equipment in a machine shop, so quite loud but also pretty constant. There are some very quick and momentary sound spikes at the location which would be nice to be able to capture but we had to work with what we had. For curiosity sake if the system was looked to be upgraded in the future to be able to measure something very fast what would you recommend?
Thanks,
Karl