Scales

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diopter

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While loading up some ammo last week I decided to check the beam RCBS 5.0.2 scale against my closet queen Pact BBKII digital scale. After an eternal wait for the digital to settle down I took the 50gr RCBS beam scale powder charge and got 49.1 on the Pact.
This Pact has never been stable under Transformer power, a fact I had forgotten.
Only under battery power was I able to recalibrate the scale which then finally gave a matching weight of 50grs.

The transformer was rated at 9VDC at 300mA. I measured 14.84VDC output using a Fluke 87 multimeter.
Hmm.....
 
Those cheap 300 mA switching power supply are notoriously bad at filtering the AC. If you checked the signal with an oscilloscope, you'd see a lot of ripple at 120Hz. Not surprising considering they cost 2-3$ in electronic surplus stores. If you had a good 9VDC power supply your PACT might very well work correctly with it.

Some of the 9V power supply for musical instruments are pretty good, but you'll pay 30-50$ for one. You can get a lot of batteries for that price. You could also probably use the +12V of an ATX (computer) power supply too if you're willing to do some soldering and have an old computer laying around.
 
VinnyQC said:
Those cheap 300 mA switching power supply are notoriously bad at filtering the AC. If you checked the signal with an oscilloscope, you'd see a lot of ripple at 120Hz. Not surprising considering they cost 2-3$ in electronic surplus stores. If you had a good 9VDC power supply your PACT might very well work correctly with it.

Some of the 9V power supply for musical instruments are pretty good, but you'll pay 30-50$ for one. You can get a lot of batteries for that price. You could also probably use the +12V of an ATX (computer) power supply too if you're willing to do some soldering and have an old computer laying around.
Click to expand...

or get 8.7v using 3.3v and 12v...
 
Space is tight as is. I keep a stock of 9V cells anyways for Chronograph, guitar pickups and alarms.
I have multiple good variable voltage and current power supplies at work, but will need to adapt a 2.1mm plug to test it. Still does not resolve my home's AC power if that is noisy.
Not about to borrow an oscilloscope from work. :)
 
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I lucked out at Addison electronics.
Was recommended a PureVolt 3V-12V Universal Adapter Model 500428( for Tablets, routers, media players, etc.) $25.00±.
Set to 9V and works like a charm. Measured 9.25V on Fluke 87 Multimeter compared to 14.84V from original transformer.
Pact scale stabilizes even faster than on battery.

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Also picked this up for the desktop.

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Samson PB15 PowerBrite Rackmount Power Center with LED Lighting
Features
19-inch rackmount power conditioner with LED lighting
Lifetime guaranteed high intensity LED lamps with dimmer control
8 rear-panel AC outlets plus an additional front-panel convenience outlet.
3-point: surge protection, peak voltage spike clamping and RFI/EMI filtering
Rear rack lighting with included LED gooseneck lamp
 
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Brought the Pact BKII to work to measure less than 1 grams weights and found that fluorescent lights still play havoc with it whereas my reloading area only uses LED and incandescent lighting.
Worked fine with 9vdc battery.
 
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It is possible you home has "noisy" power but unlikely. Those cheap switch mode power supplies are notorious. The fact yours was 14V under no load is somewhat suspect- although many times these types of supplies can't regulate well until under a load. House frequency is 60hz which is easily filtered. Flourescents with electronic ballast put off some nasty high frequency emf. Sensitive things like scales will work best on battery as you have discovered. I run my scale off a bench power supply- pretty quiet DC like a battery, but obviously a LOT more coin- but i already had it kicking around.
 
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