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Ansmann 9V rechargeable Li-ion battery in Fluke 87 - high-pitched noise

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6SN7WGTB:
Thought I'd try one of the above in my Fluke 87.

Mystified by a very high-pitched noise emanating from the multimeter, even when switched off.

Turns out it is the Lithium battery. Note that this type is 9V, not 8.4V. It's this one: https://shop.ansmann.de/en/li-ion-battery-9v-block-typ-400-min-340-mah-1pcs-cardboard-box

My (quite old) Fluke 87 draws about 9µA when 'off'

Anyone come across this?

tunk:
"Stable voltage of 9 V over 100% of the runtime."
This suggests some kind of switching step-up circuit.

Atlan:
My alkaline 9V battery for unt204 ran out.  I quickly put in a charging lipol with a changer.  Switched to current measurement, and the device showed 287. So I couldn't measure anything.  I disassembled the device to the contacts for the battery, installed 220uF, I also disassembled the battery with the inverter and put a 100uH choke there.  Such an LC filter member seems to be sufficient.  I didn't get to the tests.  But the interference no longer manifests itself.

Fungus:

--- Quote from: 6SN7WGTB on November 14, 2024, 08:48:08 pm ---Mystified by a very high-pitched noise emanating from the multimeter, even when switched off.

Turns out it is the Lithium battery.

My (quite old) Fluke 87 draws about 9µA when 'off'

--- End quote ---

Put a 1M resistor across the battery terminals and see if it makes the noise.  :popcorn:

thm_w:
If you use nimh or li-ion without active circuitry, there will be no issues with noise or interference.
The only downside with 9v li-ion is that they take a bit more effort to charge (soshine brand for example https://lygte-info.dk/review/batteries9V/Common9Vcomparator.php).


--- Quote from: Atlan on November 15, 2024, 09:59:48 pm ---My alkaline 9V battery for unt204 ran out.  I quickly put in a charging lipol with a changer.  Switched to current measurement, and the device showed 287. So I couldn't measure anything.  I disassembled the device to the contacts for the battery, installed 220uF, I also disassembled the battery with the inverter and put a 100uH choke there.  Such an LC filter member seems to be sufficient.  I didn't get to the tests.  But the interference no longer manifests itself.

--- End quote ---

Still sounds slightly risky. Who knows what measurements it might effect unless you do a full comparison.

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