Posted by No Body on September 4, 2013, 2:01 am
> This kind of advice invariable comes from someone who's never actually
> done it before. As someone who designs this stuff for a living, let's
> examine that advice a bit more.
>
> It's true that the Arduino has 8 12 bit A/D converters of the
> successive approximation type. But there's more.
>
> * Typically there are 3-4 bits of noise on the converters and/or
> reference voltage so 8 bit data is the best that one can RELIABLY get.
>
> * The input is 0-2.54 volts (unless one hacks in his own voltage
> reference which brings in its own set of problems.
>
> * The processor starts executing spurious instructions when the input
> voltage reached about 2.6 or 2.7 volts.
>
> * that channel is blown when the input reaches 3 volts.
>
> * It has practically no static or transient protection.
>
> * The input impedance varies during the successive approximation so
> the input must be driven by a low impedance source (op amp or
> instrument amp).
>
> * the input is monopolar. Bipolar (AC) inputs make the processor very
> unhappy.
>
> The field signal for each channel must be scaled or amplified as
> needed, zero offset, filtered, shaped, perhaps rectified and
> conditioned for each input port. This will cost many more dollars
> than the Arduino itself and will require a vast amount of time to get
> right. Much more money, in fact, than simply buying the proper data
> logger to fit the application.
>
> The correct answer to the OP's question should be another question,
> "What kind of physical data are you trying to capture? Most likely
> volts and amps. What else? Thermocouple input? Sunlight intensity?
> Ambient temperature? What range of temperature operation to you
> require?
>
> All that has to be known before any meaningful advice can be given.
>
> John
> John DeArmond
> http://www.neon-john.com
> http://www.fluxeon.com
> Tellico Plains, Occupied TN
> See website for email address
>
John...
Some of the concernes you raise are addressed by this system:
<https://shop.ruggedcircuits.com/index.php?main_page=product_info&products_id#>
I will often used Dallas/Maxim One-wire devices, if the temps are in a
range that they will deal with..
Then again.. a data logger for an entire Solar System.. That's one big
honkin machine!
:-)
Posted by Jim Wilkins on September 4, 2013, 12:12 pm
>> This kind of advice invariable comes from someone who's never
>> actually
>> done it before. As someone who designs this stuff for a living,
>> let's
>> examine that advice a bit more.
>>
>> It's true that the Arduino has 8 12 bit A/D converters of the
>> successive approximation type. But there's more.
>>
>> * Typically there are 3-4 bits of noise on the converters and/or
>> reference voltage so 8 bit data is the best that one can RELIABLY
>> get.
>>
>> * The input is 0-2.54 volts (unless one hacks in his own voltage
>> reference which brings in its own set of problems....
>>
>> John
>> John DeArmond
>
> Some of the concernes you raise are addressed by this system:
>
> <https://shop.ruggedcircuits.com/index.php?main_page=product_info&products_id#>
>
>
> I will often used Dallas/Maxim One-wire devices, if the temps are in
> a
> range that they will deal with..
>
> Then again.. a data logger for an entire Solar System.. That's one
> big
> honkin machine!
Neon John's comments seem to apply more to a LabJack than an Arduino.
http://labjack.com/u3
I've been using an older Radio Shack PC-interfaced multimeter to log
solar panel output. It's only one slow channel, but it's opto-isolated
for safety and ground-loop immunity and can read AC or DC voltage and
current, up to 20A. The newer model also reads temperature. There are
several less expensive versions on-line.
This decodes the serial data stream:
http://www.franksteinberg.de/SOURCE/DT9062.BAS
and here are the bit assignments in English:
http://www.multimeterwarehouse.com/TP4000ZC/TP4000ZC_serial_protocol.pdf
I've ordered one of the cheaper ones to see if I can put together a
3-channel laptop datalogger using the included software or a Basic
program and a Cardbus dual serial port.
When I was building electric vehicles I used a Campbell Scientific
datalogger to record test runs.
http://www.campbellsci.com/
jsw
Posted by Jim Wilkins on September 9, 2013, 1:27 pm
>
> I've ordered one of the cheaper ones to see if I can put together a
> 3-channel laptop datalogger using the included software or a Basic
> program and a Cardbus dual serial port.
>
> jsw
Scratch off the clunky included software which is for one meter only.
My QBasic test code that reads the older RS meter runs slowly in XP,
so this will be a DOS project, maybe using the two multimeters as
opto-isolated current sensors and my DI-194RS datalogger for DC
voltages.
http://www.dataq.com/products/obsolete/di194.html
Windows 7 includes a 6.22-style DOS that handles NTFS and long
filenames. I found it while exploring POWERCFG options and piped the
>HELP output to a file to start a manual for it.
jsw
Posted by Martin Riddle on August 5, 2013, 11:08 pm
>On Sat, 27 Jul 2013 06:09:27 -0700 (PDT), amir.zawar@gmail.com wrote:
>
>>Hi Everybody,
>>
>>I am looking for a data logger which collects data from my "Solar remote site".
>>I can visit these sites every 4 to 6 months for maintenance and need to collect data on a memory card or on the internal memory of the device in order to download them. Better will be if I could get the data over internet on my laptop as I have mobile coverage on Site (but this is not really mandatory).
>>
>>The data logger should measure and collect following data every 15 or 30 or 60 minutes:
>>- Date & time
>>- Current: between 0 A up to 250A (4 X DC channels in order to be able to measure different sources)
>>- Voltage: between 0 VDC up to 60 VDC
>>- Temperatures: between -5°C up to 55°C (3 or 4 channels in order to measure outside, inside, battery temp)
>
>With what you've specified, you need 9 channels. That would push you
>into the expensive world of 16 channel data loggers. If you drop a
>temperature channel (you really don't need battery temperature) then a
>much less expensive data logger can be used.
>
>We need some more data before any hard recommendations can be made.
>For instance. do the inputs have to be isolated? That is, do they
>need separate grounds? If so that pushes the cost up significantly.
>
>If you can arrange your circuitry so that all inputs share a common
>ground then you can use a relatively inexpensive common ground system.
>
>Here's a typical relatively low cost unit.
>
>http://www.omega.com/pptst/OM-CP-OCTPROCESS.html
>
>8 channel, current input, lithium battery powered, data collected via
>a PC. Enough memory to do 16 samples per hour for 6 months (if I did
>my math correctly).
>
>Most any variable can be easily converted into a current with low
>noise. That's why 4-20 ma is so common in industry.
>
>In this case, a simple series resistor would convert the 60 volts to
>say 1 ma. For current, either a shunt or a hall effect device
>measures the current and its output is converted to a current with a
>simple resistor.
>
>For temperature you can go simple and use a thermistor scaled and
>linearized to output a current. This device allows one to store
>per-channel scaling factors so the actual value doesn't matter much.
>
>Or you could go a bit more complicated and use an LM35 temperature to
>voltage IC
>
>http://www.ti.com/product/lm35
>
>The voltage output is again converted to current with a resistor. This
>(and the thermistor, for that matter) will require a small amount of
>power. You can rob that from the 60 volt input using a zener diode in
>parallel with the LM35 to keep the supply voltage stable..
>
>The LM35 draws worst case 136uA and needs from 5 to 15 volts to
>operate. I'd choose 15 volts to get the maximum range. The resistor
>is 60-15 = 45 volts /136uA = 330kohms. That would dissipate 6 watts.
>If your typical supply voltage is different than 60 volts then just
>substitute the numbers.
>
>This post isn't designed to answer your question directly. It's
>designed to get you thinking in the right direction. If you google
>"battery powered 8 channel data logger", you'll find hundreds of
>varieties. The Omega one was simply one of the first hits.
>
>John
>John DeArmond
>http://www.neon-john.com
>http://www.fluxeon.com
>Tellico Plains, Occupied TN
>See website for email address
Labjack looks good too. I havent personally used them, but I've heard
good things...
<http://labjack.com/>
Cheers
Posted by Mr Clarke on August 7, 2013, 7:41 pm
>
>>On Sat, 27 Jul 2013 06:09:27 -0700 (PDT), amir.zawar@gmail.com wrote:
>>
>>>Hi Everybody,
>>>
>>>I am looking for a data logger which collects data from my "Solar remote
>>>site".
>>>I can visit these sites every 4 to 6 months for maintenance and need to
>>>collect data on a memory card or on the internal memory of the device in
>>>order to download them. Better will be if I could get the data over
>>>internet on my laptop as I have mobile coverage on Site (but this is not
>>>really mandatory).
>>>
>>>The data logger should measure and collect following data every 15 or 30
>>>or 60 minutes:
>>>- Date & time
>>>- Current: between "0 A" up to "250A" (4 X DC channels in order to be
>>>able to measure different sources)
>>>- Voltage: between "0 VDC" up to "60 VDC"
>>>- Temperatures: between "-5°C" up to "55°C" (3 or 4 channels in order to
>>>measure outside, inside, battery temp)
>>
>>With what you've specified, you need 9 channels. That would push you
>>into the expensive world of 16 channel data loggers. If you drop a
>>temperature channel (you really don't need battery temperature) then a
>>much less expensive data logger can be used.
>>
>>We need some more data before any hard recommendations can be made.
>>For instance. do the inputs have to be isolated? That is, do they
>>need separate grounds? If so that pushes the cost up significantly.
>>
>>If you can arrange your circuitry so that all inputs share a common
>>ground then you can use a relatively inexpensive common ground system.
>>
>>Here's a typical relatively low cost unit.
>>
>>http://www.omega.com/pptst/OM-CP-OCTPROCESS.html
>>
>>8 channel, current input, lithium battery powered, data collected via
>>a PC. Enough memory to do 16 samples per hour for 6 months (if I did
>>my math correctly).
>>
>>Most any variable can be easily converted into a current with low
>>noise. That's why 4-20 ma is so common in industry.
>>
>>In this case, a simple series resistor would convert the 60 volts to
>>say 1 ma. For current, either a shunt or a hall effect device
>>measures the current and its output is converted to a current with a
>>simple resistor.
>>
>>For temperature you can go simple and use a thermistor scaled and
>>linearized to output a current. This device allows one to store
>>per-channel scaling factors so the actual value doesn't matter much.
>>
>>Or you could go a bit more complicated and use an LM35 temperature to
>>voltage IC
>>
>>http://www.ti.com/product/lm35
>>
>>The voltage output is again converted to current with a resistor. This
>>(and the thermistor, for that matter) will require a small amount of
>>power. You can rob that from the 60 volt input using a zener diode in
>>parallel with the LM35 to keep the supply voltage stable..
>>
>>The LM35 draws worst case 136uA and needs from 5 to 15 volts to
>>operate. I'd choose 15 volts to get the maximum range. The resistor
>>is 60-15 = 45 volts /136uA = 330kohms. That would dissipate 6 watts.
>>If your typical supply voltage is different than 60 volts then just
>>substitute the numbers.
>>
>>This post isn't designed to answer your question directly. It's
>>designed to get you thinking in the right direction. If you google
>>"battery powered 8 channel data logger", you'll find hundreds of
>>varieties. The Omega one was simply one of the first hits.
>>
>>John
>>John DeArmond
>>http://www.neon-john.com
>>http://www.fluxeon.com
>>Tellico Plains, Occupied TN
>>See website for email address
>
> Labjack looks good too. I havent personally used them, but I've heard
> good things...
> <http://labjack.com/>
>
> Cheers
You make it and I`ll make a better one and sell millions of them!
XML site map
> done it before. As someone who designs this stuff for a living, let's
> examine that advice a bit more.
>
> It's true that the Arduino has 8 12 bit A/D converters of the
> successive approximation type. But there's more.
>
> * Typically there are 3-4 bits of noise on the converters and/or
> reference voltage so 8 bit data is the best that one can RELIABLY get.
>
> * The input is 0-2.54 volts (unless one hacks in his own voltage
> reference which brings in its own set of problems.
>
> * The processor starts executing spurious instructions when the input
> voltage reached about 2.6 or 2.7 volts.
>
> * that channel is blown when the input reaches 3 volts.
>
> * It has practically no static or transient protection.
>
> * The input impedance varies during the successive approximation so
> the input must be driven by a low impedance source (op amp or
> instrument amp).
>
> * the input is monopolar. Bipolar (AC) inputs make the processor very
> unhappy.
>
> The field signal for each channel must be scaled or amplified as
> needed, zero offset, filtered, shaped, perhaps rectified and
> conditioned for each input port. This will cost many more dollars
> than the Arduino itself and will require a vast amount of time to get
> right. Much more money, in fact, than simply buying the proper data
> logger to fit the application.
>
> The correct answer to the OP's question should be another question,
> "What kind of physical data are you trying to capture? Most likely
> volts and amps. What else? Thermocouple input? Sunlight intensity?
> Ambient temperature? What range of temperature operation to you
> require?
>
> All that has to be known before any meaningful advice can be given.
>
> John
> John DeArmond
> http://www.neon-john.com
> http://www.fluxeon.com
> Tellico Plains, Occupied TN
> See website for email address
>