PPK2 measure low power from peltier module

RE: PPK2 measure low power from peltier module

Pema — Thu, 01 Jul 2021 07:18:43 GMT

Hi,

Jumping in on this thread...

So is my understanding correct that when using amp meter mode from a battery, the current measurement will be correct (using the Rc resistance), but another ~40uA will be taken from the battery (outside the current measurement) which goes through the two branches of 120k+30k each?

Regards,

Peter

RE: PPK2 measure low power from peltier module

larryd — Wed, 23 Jun 2021 04:39:41 GMT

ok thanks. I'm now seeing max 0.18µA for my first tests, enough to keep me moving forward. thank you for your help.

RE: PPK2 measure low power from peltier module

hmolesworth — Tue, 22 Jun 2021 23:41:26 GMT

Good news, thanks for update.

Note if the peltier or other voltage generator (piezo, etc) is one of the tiny low-current versions it's possible that the loading of the PPK-II is too much for the module as there are two voltage dividers for voltage measurement to calculate current via (Vout-Vin)/Rc which is (120k + 30k) || (120K + 30k ) = 75k to Gnd, so at 3 volts that sinks 40uA with nothing connected to Vout. I updated the diagram to show the current sense resistor as well:


data-mode="c_cpp">// Resistor Rc for current sense is 1k0 in parallel with one or more of 110R, 11R0, 1R0 and 0R051 +ve Supply to DUT From VOUT                               External Battery +ve To VIN --------------------+                             +-----------------------+ |                             |                       | +---------+     |                             |     +---------+       | |     GND |     | VOUT                   VIN  |     | GND -ve |       | |    +====O=====O=============================O=====O====+    |       | Battery |    |    |    |     #----+                        |     |    |    |       | + 3 volts |    |    |    |     |    |Rc        AMPERE \      |     |    |    |     +-O-+ |    |    |    |     |   +++                 \     |     |    |    |     |   | |    |    |    |     |   | |   +-----------O  O----#     |    |    |     |   | |    |    |     |   | |   |                   |     |    |    |     |   | |    |    |    | 120k|   | |   |                   |120k |    |    |     |   | |    |    |    |    +++  +++   |   \  SOURCE      +++    |    |    |     |   | |    |    |    |    | |   |    |    \             | |    |    |    |     +-O-+ |    |    |    |    | |   +----#--O  O-- PPK LDO  | |    |    |    |       | Gnd (-) |    |    |    |    | |                           | |    |    |    +-------+ |    |    |    |    +++                           +++    |    | |    |    |    |     |                             |     |    | |    |    |    |     #-- VDUT                VIN --#     |    | |    |    |    |     |  Sense                Sense |     |    | |    |    |    |    +++                           +++    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    +++                           +++    |    | |    |    |    |     | 30k                     30k |     |    | |    |    |    +--#--+                             +--#--+    | |    |    |       |                                   |       | |    |    |     =====      <<== Common Gnd ==>>     =====     | |    |    |      ===           (Common -ve)          ===      | |    |    |       =                                   =       | |    +===================================================+ |     PPK-II

RE: PPK2 measure low power from peltier module

larryd — Tue, 22 Jun 2021 22:35:10 GMT

The graphs were empty (live enabled) however the dashboard window was showing values for average, max etc. I restarted the software and it is now working as anticipated. thank you.

RE: PPK2 measure low power from peltier module

larryd — Tue, 22 Jun 2021 21:06:16 GMT

The diagram helped, I now at least can get readings from a battery, just not the micro amps that a handheld meter gives me when testing the peltier. thank you.

RE: PPK2 measure low power from peltier module

hmolesworth — Tue, 22 Jun 2021 15:18:16 GMT

Perhaps turn on the slider on the App after setting Ampere Mode - see my notes ppk-2-not-passing-through-external-power-in-amp-mode