Totem Mini Lab – New review
As I wrote yesterday, I received a replacement Lab Board. Today I’m testing it by repeating the tests I did for the first full review. First I will give you the conclusion, the details are below the conclusion.
- The idle voltage and current measurements issues have been solved.
- The user interface for the setting of the DAC voltages has been improved, it still rolls to zero volts when one reaches the maximum, but we now have the ability to roll back over zero to get back to the maximum.
- The TotemDuino now registers a com port and connects to my MacBook Pro.
- The documentation about the construction materials, however comprehensive, is good, it shows the ways parts can be combined.
- A built structure is pretty sturdy, better than I expected.
- The voltage measurement has pretty good, for a reasonably simple Voltmeter.
- The frequency measurement precision was a pleasant surprise; it even improved with the new Lab Board
- The DAC’s give out voltages, now within 0,5% of their set values.
- The documentation about the electronics part of the Mini Lab board is obviously written by engineers. The kit would really benefit from more extensive explanation – with examples – of the functions of the Mini Lab board! Especially before it can be released into the hands of beginners.
Contact with the Totem team
The Totem team responded adequately to the feedback. They are working on the documentation and on beginner’s lessons to be used with the Mini Lab and its Side Panel. A second Side Panel is in the works, and what I’ve seen from it, it will be a nice addition to this experiment rig!
Renewed review details
I compared the current measurement from the Mini Lab with my bench multimeter. In idle mode, nothing connected, the board now correctly shows 0 mA (last three digits on the 7-segment displays). When I connect LEDs and 270 Ω resistors, the readings on the Lab Board and the bench meter can be seen in the images below. All in all a lot better than last time!
I also repeated the voltage measurement with pretty good results. I calculated the precision per range and put the results in a table. See pictures below (you should look at the first three digits on the 7-segment displays). The average deviation in the 0,5 Volt range is 0,5%, in the 5 Volt range it’s 0,25% and in the 50 Volt range it’s -0,8 %. A lot better than the previous test.
In the new frequency measurement test the board performed even better than last time. The overall precision was 0,04%. See pictures and table below:
The Mini Lab has three programmable voltage outputs, DAC1-DAC3. They all can be set from 0 to 3.30 Volts (look at the middle three digits on the 7-segment displays). I tested them. I set DAC1 to 0,77, DAC2 to 2,22 and DAC3 to 3,22 Volts. Then I measured the actual values with my bench meter.
|set Voltage||bench meter||precision|
|0,77 V||0,76599 V||+/- 0,5%|
|2,22 V||2,22924 V||+/- 0,4%|
|3,22 V||3,2001 V||+/- 0,6%|
All in all, nice results.
The annoying little glitch I spoke about has been solved in such a way that when it rolls over 3,3 Volts you can now roll it back from 0 to 3,3 again.
DAC measurement pictures