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

[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]

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'

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

[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).

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.

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

[daisizhou]

You need to add a transistor. See the circuit below. You can try to copy it. This is an open source project.
https://www.mydigit.cn/thread-163962-1-1.html

[6SN7WGTB]

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'

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

Yes, will do when I have finished doing a capacity measurement on the electronic load. It's silent at 25mA...

Most likely it is the boost regulator, which does not 'like' low current draw. 'Like' being a non-technical explanation.

[Hydron]

I'm using an Ansmann 8.4V NiMh LSD battery in my Fluke 87 V. Nothing in there other than 7 cells, no noise and very compatible with 9V (an alkaline will drop to a similar voltage after some use).

You can also get a LiPo equivalent (2 cells in series, no DC-DC/charger) but they do go down quite low in voltage when near empty, so the gear needs to handle this (can just test with a PSU first), and you also want to get one with the right shape (mine came with very sharp corners on the case instead of the rounded normal 9V shape, and won't work in some items due to this).

[AVGresponding]

Thought I'd posted a reply in here, but was a similar thread   
https://www.eevblog.com/forum/testgear/use-of-rechargeable-batteries-in-test-equipment/msg5718069/#msg5718069