Why no bird 43 power supply?

[groundwire]

Other than the portability issue, why hasn't bird, or anyone for that matter come up with a power supply solution (walwart type) for the bird 43 pep kit? Constantly changing 9v batteries and the possible accuracy issues (if any) due to dying 9v batteries is a drag. I have not checked if the two 9v batteries are in series or parallel but either way it shouldn't be hard to find a 9vdc or 18vdc walwart to power the meter. Maybe it would introduce noise into the circuit thus giving false readings? All other pep meters on the market use an external power supply, why not bird? Thoughts?

 

[DoctorAudio]

It's a split rail supply with +9V and -9V on each side of ground. It could be done with two equal 9V wall warts with the second supply wired in reverse.

 

[Low_Boy]

The older birds were a bad design with the light on the side. You can go through battereies like crazy. Especially if it is sitting close to something you can't see the light.

 

[Chris Lawrence]

I guess I’ve never thought of this but, if you simply remove the light and keep the peak switch on, will it still draw power and quickly drain the battery?

 

[nomadradio]

Bird's original peak-reading circuit used an obsolete operational amplifier (op-amp) chip, the type 709. It's a power hog, only works with a split bipolar power supply and is easily 'bled' by stray RF, causing erratic readings.

Aftermarket replacements for this accessory use a lower-power opamp that will function from a single battery.

Biggest reason I found not to use an external DC power pack was RF pickup. Any RF in the room would find its way into the peak circuit through the DC power cord. Your first clue will be to see the meter peg out when the true reading should be far less.

We use a rechargeable 9-Volt battery to power our peak adapters. It gets changed out once a week, and put on the charger. A fresh one goes in. Only drawback is that leaving it in "peak" mode overnight too many days in a row runs it down in less than a week. A LED will draw about the same current as the LM358 opamp chip, so I declined to double the power drain with a pilot light. Eventually I got in the habit of checking the peak/average switches on the wattmeters before closing up and going home for the day.

73