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in Vehicle tracking by anonymous

Hi 

I am using FMC130 device. The questions are:

1. Why analog reading for AIN2 without any input is 262mV? and 

2. after testing with different voltage inputs the analog average readings for AIN2 is 183mV?
 

Teltonika (Output) Multimeter (Input) Voltage Offset
1529 1357 172
1514 1327 187
1412 1236 176
1180 1001 179
948 762 186
738 549 189
729 539 190
655 471 184
609 417 192
581 403 178
568 388 180
Average 183

1 Answer

0 votes
by anonymous
Hello.

FMC130 has an additional error on Analog input on range 12V and on range 30V:

https://wiki.teltonika-gps.com/view/FMC130_General_description#Electrical_characteristics

Input resistance on AIN is 150 kOhms, while input resistance of typical multimeter is about 10MOhms, therefore readings may be different.

Your method is very good. Having measured additional error you can correct voltage readings on your server side.

Regards
by anonymous


1. How can we correct the voltage readings on our server-side? and

2. the readings from the multimeter and AIN is different because of the resistance. but without connection, it still has offset, and the offset is not consistent. our objective is to understand how do we get a correct one if there is no fixed offset that we can use to correlate?

by anonymous

How can we correct the voltage readings on our server-side? - subtract 183mV from the voltage reading or if more accuracy is needed prepare offset table (as you already did) based on FM tracker readings and certified multimeter readings and use calculated offset for each range.

The case when AIN is not connected schould not be considered, voltage schould be read from voltage source, positive wire of measured voltage source schould be connected to AIN and negative to device GND.