handheld LCR meter more accurate on battery power?

[dai h.]

is there any technical reason a handheld LCR meter would be more accurate on battery power? On the 10Megohm range on mine, the 2% (plus number of digits) accuracy is qualified in the instructions where it states, "specifications met only on battery power". Also, I have this vague recollection where I quickly checked some precision low value Rs (say 0.25% tol.) very soon after I purchased them, and they seemed to be very close where as powered by a (switching AC adapter) it seems the reading would drift and change (over a number of hours, taken the following day, etc. comparing to what I wrote down for a specific R)--but maybe that is just some misperception or some sort of wishful thinking on my part. Basically if there actually is a real reason the readings would be more accurate, then I was considering powering the meter off of rechargeable 1.2V in series (x10 for 12VDC). Thanks!

[satsloader]

Did the LCR's readings fluctuate in sych with the wall's a/c fluctuation? If so, the meter's regulation is poor. In a sense it's sample rate is too sensitive. The dc solution would overcome that, so I'd think saving the time spent averaging the wall wart's errors is worth the effort. Make it road worthy!

Bill in P.G.

[Steve Conner]

That doesn't make sense, because if the regulation was poor, the readings would also drift as the battery ran down.

So, it must be noise from the adapter, if it's a switching type. Try a better quality one with linear regulation. You might also like to try grounding the negative output to the ground prong of the wall plug, which would reduce hum pickup compared to a two-prong adapter. These tend to induce hum as they have an internal circuit not unlike the old "Death cap" amps.

That is, if it needs it. Maybe the noise is only a problem on the high resistance range. It would make sense that the highest range was the most sensitive to noise pickup.

[dai h.]

thanks guys.

satsloader(Bill),

as far as the readings fluctuating along with the AC, I have no idea since I've never tried monitoring the AC while reading parts.

fwiw, the switching AC adapter I'm using is this one:

超小型スイッチングＡＣアダプタ　１２Ｖ ０.４Ａ（入力ＡＣ１００〜２４０Ｖ）　内径２．１ｍｍ　Ｇ� o０５−ＵＳ１２０４: 電源一般 秋月電子通商 電子部品 ネット通販

(according to the page above) it's regulated, and specs are 12V 0.4A(400mA) while the LCR meter instructions specify "DC12V 50mA", so it doesn't appear much of a strain on the adapter.

Steve,

so would it be safe to say the (residual high frequency ripple?) contributes(or can) to imperfect operation? (And therefore a linear regulator-equipped supply which I gather has less noise would help?) As far as a ground, there is a ground/guard banana plug jack right next to the plugs for the leads, and I have used that before (connecting to a wall socket AC safety ground) but not really sure it makes a difference. The Cs and Rs I've tried to match do seem to be matched when I've taken readings the next day or whenever, but the readings can be different. I'm thinking I shouldn't expect too much since it's not a "lab grade" unit (which from what I've seen would cost thousands of $$$) but just trying to figure out if there is something I can do (within reason) to try to maintain consistency. I've bought a single or couple precision (0.25%, 0.1%, etc.) Rs when I could find them to check out how they read and it's kind of geekishly interesting.