[Amps] RMS VS Peak VS Average power and the Bird 43 wattmeter

[Will Matney]

Dennis,

Kind of odd aint it, one would think that would nuke the rf in it's tracks at the jack. Probably to do this then, a pi filter would have to be added or something similar. I wonder what the capacitance was he used? The reason being, I've seen other meters using similar setups with no problems at all. Of course the Ni-Cads will work fine. Just have to take them out all the time to recharge them unless you might rig that jack up for the charger to plug in. When in use, just unplug it. At least you wouldn't have to fool around with taking the batteries in and out. How much life does the batteries give between charges and what would the life be on an alkaline in the Bird?

Best,

Will

*********** REPLY SEPARATOR ***********

On 3/30/05 at 12:15 PM Dennis12Amplify at aol.com wrote:
In a message dated 3/30/05 10:17:25 AM Central Standard Time, craxd1 at ezwv.com writes:
Dennis,

You should be able to bypass the hot lead on the inside with a 1000 to 4700 pF cap to ground I would think. The ground on those mono jacks go directly to the chassis. If it were a stereo jack, use a cap on both leads to the chassis. That ought to shunt any RF to ground and keep it out of the circuitry.

Best,

Will
Will,

 My friend had bypass caps there.

 The problem stemmed from the fact that there was a standing wave on the line and with the connection thru the wall wart to ground, the shield current split into two paths causing the Bird element to read incorrectly. Switching to rechargable 9V batteries and unplugging the external power when making a measurement allowed him to make accurate mesaurements again. 

 With no standing wave present, like into a Bird dummy load, the readings were very close to normal, but still somewhat lower than they were supposed to be.

 So I'll stick with the basic system, and only turn it in when making the peak measurement and remember to turn it right back off again.

 I designed and built a peak detect circuit for another friend that used a micropower op amp and he gets about 1 year of continuous operation out of it. No need for a power switch in that case; just replace the SINGLE 9V battery once a year!

 If times get tough here, I may adapt the design to a PC board and sell 43 retrofit peak kits in competition with Bird. If I can have the same or better accurcy as them, and a 1 year battery life, I believe there's a market for it.

Regards,

Dennis O.