Vacuum/pressure transducer testing

[bughood]

I have a Verus Pro and an eepv 302 AL Snap on transducer. My question is what does everyone else get for a maximum reading for vacuum? It says it should read to 20 inHg. I thought the one I had was bad so I had it warranteed. The new one is worse. My old one would read 14.4 max and the new one reads 13.9 max. In both cases I used a vacuum pump with a guage plus a separate vacuum guage to double check. I can max the pump out to 22inHg and the max reading is 13.9inHg. Yes I calibrate the transducer before every test. Shouldn't it read at least 20inHg if that is supposed to be the range?

Thanks and Merry Christmas to all

[Harley Mike]

The reading is probably in PSI or -PSI . You have to convert that to in.hg. It's roughly double. My WPS 500 reads the same way. Example -10 psi is roughly 20 in.hg. Hope that helps.

[bughood]

I'm using the Snap on menu set up for vacuum. It says I'm reading in vacuum not pressure.

[bughood]

Another note, the readings are fairly accurate until I get to 12inHg.

[Witsend]

I wouldn't sweat it and would assume that even though the pressure transducer is capable of reading a negative pressure, it is really just purpose built to accurately measure a positive pressure from zero to whatever it is rated to max at

[maven]

I wouldn't sweat it and would assume that even though the pressure transducer is capable of reading a negative pressure, it is really just purpose built to accurately measure a positive pressure from zero to whatever it is rated to max at

In a mind boggling change of events Im going to agree with Wit here. they are sold as pressure transducers, and seem to display pressure referenced to atmospheric, they dont to be displaying absolute pressures, and they dont list an actual definitive vacuum spec that I see. Its sold as a 0-100psig sensor. Id consider the vacuum a nice bit if overrun but wouldnt rely on it for diagnosis, and instead pickup either a Fluke one that actually lists precise specs for pressures below 0psig or assemble my(your) own from commercially available transducers from Omega, Johnson Controls and the like.

[wagzilla]

I'm using the Snap on menu set up for vacuum. It says I'm reading in vacuum not pressure.

question what is your altitude ? is it higher then sea level? Then your numbers would be lower

James

[bughood]

We are around 1300 ft.

[bughood]

?????

I think you guys are missing the point. The menu says 20inHG. If that is what it says it should do that is what I expect. Why is that to much to ask? If your scan tool said it could read data from a 2012 Chevy but could only read through 2000 wouldn't you be upset?
I spent a lot of money on this and expect to get what I paid for! If it can't then give me my money back and I will get a Pico. I tried the Fluke and the noise was horrible.
All I asked was for others to duplicate my test and get back to me. Does no one have this transducer to duplicate my test?

[maven]

I think you guys are missing the point. The menu says 20inHG. If that is what it says it should do that is what I expect. Why is that to much to ask? If your scan tool said it could read data from a 2012 Chevy but could only read through 2000 wouldn't you be upset?
I spent a lot of money on this and expect to get what I paid for! If it can't then give me my money back and I will get a Pico. I tried the Fluke and the noise was horrible.
All I asked was for others to duplicate my test and get back to me. Does no one have this transducer to duplicate my test?

Im not missing the point at all...I told you what I believe the issue is. SnapOn doesnt advertise this transducer as having any specific vacuum range, they dont inform of its accuracy below 0psi, they dont even actually call it a vacuum sensor. Its labeled as 0-100psi. Other manufacturers and other transducers are specifically labeled as vacuum transducers, or call out clearly the range of vacuum and pressure they measure.

While the scan tool may be able to display 20"hg if it recieves that data, this sensor doesnt appear to be sending out signals for that level of vacuum.

Would you blame the scope for not being able to display temperature if you had voltage probes hooked up instead of a thermocouple?


Its a sucky situation but if you need accurate vacuum reading you need to purchase a transducer with specification that cover the range you need.

[greasybob]

Vacuum sample with filter on. what do you need to know exactly? What were you testing ? Did you calibrate sensor ? Need more samples ?

[diesel71]

another sample, like bob asked are you calibrating the sensor before use ?
20150127-0014-1.jpg

[greasybob]

You can also leave the scope in the 100 psi setting in a 25 psi scale. Just multiply by 2 to get inHg.

[bughood]

Thanks Greasybob and Diesel71. That's what I'm looking for. Our local Snap-on tech rep got back to me today. He said Snap-on changed who made the transducers for them some years back. It sounds like that is the problem. Are your transducers older than a few years? Thanks again.

[bughood]

And yes I always calibrate the transducer.