0

multimeter and fona
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

multimeter and fona

by tnts on Tue Aug 22, 2017 7:44 am

Hi,

I have something weird:
I inserted M-3650 multimeter inline with battery and FONA808 to measure current.
When meter is between inserted fona restarts. Does not obtain network login.
When I remove the meter all works fine.

Is it due to current-meter giving too much resistance, resulting in voltage drop?
Any ideas?

tnts
 
Posts: 172
Joined: Thu May 18, 2017 4:17 pm

Re: multimeter and fona

by tnts on Tue Aug 22, 2017 7:50 am

I will answer to me myself :)
I checked a manual for my multi-meter: 300mV for 2A current voltage drop to be expected.
Fona can produce high amp peaks.
I am guessing, it is interpreted as "under voltage" by Fona.

tnts
 
Posts: 172
Joined: Thu May 18, 2017 4:17 pm

Re: multimeter and fona

by adafruit_support_mike on Wed Aug 23, 2017 12:01 am

Yep, you have the right answer.

The FONA's burst current when talking to a cell tower is high enough to generate a fairly large voltage across a current-sense resistor.

adafruit_support_mike
 
Posts: 49331
Joined: Thu Feb 11, 2010 2:51 pm

Please be positive and constructive with your questions and comments.