"Looking at the data sheet for the ADC, I see that given the reference of 3.3v, anything above that would indeed result in a maxed out reading (4095), so my reading is at least making sense given what the ADC is measuring. That still leaves the…"
"Has anyone seen the case where disconnected the airspeed reading is 4095? That is what I am getting. If I test it with a DMM, no sensor connected, the airspeed analog pin on the Oilpan is reading 4.55 volts. Not sure why the ADC is reporting this as…"
"I just measured my MPXV7002DP.
With 5.06 volts in, analog reads 2.45 volts, which is pretty close to the spec sheet.
I measured this open circuit with a DVM.
I guess the "sensor unconnected" readings that you get from the ADC has…"
"I have not tested the MPXV7002DP. I was reading from the spec sheet where it makes a point of having a 2.5 volt output at zero pressure (assuming 5 volt supply).
I am using a MicroBridge sensor that has a range of 0 to 250 Pa over a 0.5 volt to 4.5…"
"OK. I didn't know that about a disconnected sensor. But, a connected sensor that has a zero offset of Vcc/2 will have an ADC reading of...
((Vcc/2)/Vcc)*4096 = 2048
and so will be shown as disabled. Isn't…"
"That'd work for me, but I'd hate to special case my situation. My disconnect values for the 7002 where in the 2800s. Maybe it's related to the load on my board as I'm also running a uBlox, compass, current, and XBee P900."
"Basically, I took a big stack of APM boards and a big stack of 7002 and 5004 sensors and tested all the combinations, creating a spreadsheet of all the results. Typical values for the "no airspeed" were in the 2700s. 5004s were in the…"
"A little while back I posted some detailed instructions to test the air speed sensors using a meter as Doug had said above, I listed the expected results on the unit and the pins to be tested, it might help to take a…"
Just curious how it was determined that >3000 would be the right value to expect from the airspeed sensor to indicate that it's connected. I have a APM 1.0 running 2.12 and MPXV7002DP sensor, and after trying 4 different BECs, I can only achieve an output >3000 with 1 bec. The lowest output I got was 2950. I've changed the value to 2940 to make sure things work for me, but I'm curious as to how it was set at 3000.
"So it turns out that the value that's getting read off is too low. Depending on what kind of BEC I use, I can get values ranging from 2940 on higher. I just have to lower the 3000 value that's being used now to determine if it's…"