UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - AD8307 probe-How is it used?

G0HZU_JMR · 24th Oct 2021, 2:51 pm

The AD8307 can certainly give really good results but I think it's important to understand its limitations when it is fed something other than a sine wave.

It definitely will fall over if given a signal with odd order harmonics like a square wave and theory suggests the error is 3dB in this case. That's a lot worse than other types of meter. I definitely wouldn't advise using an AD8307 to measure the power of audio test signals unless a pure sine wave was used.

Here's a screenshot of my old software after testing my AD8307 sensor back in 2019. Hopefully I used a lowpass filter after the sig gen although that sig gen does already have low harmonics. I can't remember what the test frequency was but you can see the AD8307 did quite well in this test. The detector linearity isn't that great but for most things this doesn't matter.

24th Oct 2021, 2:51 pm	#27
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: AD8307 probe-How is it used? The AD8307 can certainly give really good results but I think it's important to understand its limitations when it is fed something other than a sine wave. It definitely will fall over if given a signal with odd order harmonics like a square wave and theory suggests the error is 3dB in this case. That's a lot worse than other types of meter. I definitely wouldn't advise using an AD8307 to measure the power of audio test signals unless a pure sine wave was used. Here's a screenshot of my old software after testing my AD8307 sensor back in 2019. Hopefully I used a lowpass filter after the sig gen although that sig gen does already have low harmonics. I can't remember what the test frequency was but you can see the AD8307 did quite well in this test. The detector linearity isn't that great but for most things this doesn't matter. Attached Thumbnails __________________ Regards, Jeremy G0HZU