Author Topic: Qoitech Otii  (Read 2169 times)

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Offline mikeselectricstuff

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Re: Qoitech Otii
« Reply #25 on: January 30, 2019, 12:38:55 pm »
I've looked at this problem a few times over the years.
My conclusion is that the easiest way to do it is to use a voltage regulator with a consistent, known quiescent current, and measure the input current. This addresses the issue of voltage drop across a sensing resistor.
To deal with the wide range, about 3 sensing R's in series, with bypass diodes to limit the voltage across them to about 1V.
Measure the voltage across all 3 simultaneously, and select the one that's in range.

I've also looked at the "charge bucket" approach with capacitors, but leakage and nonlinearities make this a non-starter

In practice it is often possible to avoid the need for special testgear by manually forcing various modes, measuring the current in each, then looking at the time spent in each mode in normal operation.
Batteries are not precision devices, so you don't need to measure avarage draw accurately - 10% is easly good enough
 


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Offline jeremy

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Re: Qoitech Otii
« Reply #26 on: January 30, 2019, 12:56:57 pm »
Yes, I agree that 10% is probably ok for most applications. Sadly though, a lot of these instruments do give people a false sense of security about how precise batteries are, and of course nobody is going to correct them if it sells less meters...

I recently read a R&S white paper on measuring radio module current and estimating battery life. It was basically just: if you buy our $50k instrument, it will tell you that your device sending a tiny packet once per week can last 19 years on a rechargeable lipo(assuming no self-discharge) :palm:
 

Offline Apollyon25_

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Re: Qoitech Otii
« Reply #27 on: January 31, 2019, 12:35:55 am »
At one of my work places, we have two Otii Arc's, and I've found them extremely versatile for measuring the current consumption of our IoT remote trigger device.

We've used it to qualify our coin cell battery (Primary Li), optimise our FW for sleep mode currents and wake periods, as well as characterise the various operating modes we'd see while awake.

I've used it to fix a quirk with our implementation of an ST Microelectronics battery charger IC, used with a larger Li-ion battery pack, and have used it as a general PSU and volt/current meter a few times. I've used its GPIO and ADC/Sense channels just as a readily useable scope/logic analyser...

I've used it to qualify our changes to our app, between various versions of the Tizen OS on the various generations of the Samsung watch, and it's been used to direct how our app behaves to obtain the best battery life without limiting our product features too much.

Sure, the scripting is a premium feature, and you pay for this with a subscription model. This isn't too different to many software licencing arrangements, and I can understand some people's reluctance to support such a sales model.

I've found their support exemplary! They've helped debug my setups, my scripts, and they've updated FW and app for me specifically to address any issues I've come up against. They take UI improvement suggestions on-board, and even updated me when a few of these were implemented.

I looked at a bunch of Keysight gear to do much the same (battery emulation) and I needed three bits of kit and none of them were cheap.

It works for me.
 
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Offline EEEnthusiast

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Re: Qoitech Otii
« Reply #28 on: May 01, 2019, 05:45:37 am »
You might want to consider the ZS-2102-A from ZSCircuits. It does what the Otii Arc can do and much more. It has a higher bandwidth with a pulse response time of < 2uS. It samples at 1Msps and has a dynamic range of -1A to 1A. With 1uA accuracy and less than 100nA resolution for average measurements. It can measure negative currents as well which is useful in some IOT devices which may use solar cells or buck boost converters which can feed currents back to the battery. And the software is free.
 
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Offline julianhigginson

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Re: Qoitech Otii
« Reply #29 on: August 12, 2019, 05:05:56 am »
I saw this today, and was really interested in it at first glance, but soured a bit on further reading.
I figured someone on here would have has some opinions already.. ;-)

The sampling rate is a bit lower than I'd prefer, but the breakdown between basic features and subscription features is the dealbreaker.  It's a shame, because with battery profiling/simulation capability outside the subscription model, it'd be pretty much perfect for a lot of things I've worked on in the past and will work on in future.

I see the point of needing an ongoing income source for keeping computer software (which is a major component of this instrument by the looks of it) up to date and working and growing...  it just seems that this isn't making the tradeoff quite right. Especially for a small company with just one product that we have no guarantee will even be around in another year.
 

Offline julianhigginson

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Re: Qoitech Otii
« Reply #30 on: August 12, 2019, 05:07:40 am »
that zscircuits option looks interesting.
 

Offline EEEnthusiast

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Re: Qoitech Otii
« Reply #31 on: September 12, 2019, 07:12:12 am »
I forgot to mention that I am the designer for the ZS-2102-A. My apologies.
 


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