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Measuring Solar Radiation based on Photovoltaic Cells
#46

Hi,

(12-06-2015, 17:43)hvalentim Wrote:  That material seems to be here.

Thanks hvalantim. Yes, that's the material I had seen (and I believe Werk is referring to below), but I couldn't find it again.

(03-06-2015, 17:33)Werk_AG Wrote:  I know that I'm using on this, the most simplest OP amplifier circuit possible, a single stage non inverting amplifier, and that a lot better can be done, but this way, for start, almost everybody could understand how it works ......

Somebody published (many thanks for that) the schematic of a reputable brand solar radiation sensor, the first stage amplifier uses what seems to me an integrator configuration. ..... could you please just calculate the used gain for me? Do you find the formula, or wish I put it here?

Yes, you make some very important points in that post (#35), particularly concerning the circuit being easy to understand. But I'll try to explain why Davis (for example) do it slightly differently (using the negative input of an Op-Amp), and to answer your questions above.

Almost the complete circuit (a supply decoupling capacitor would be wise) is as follows (cut from the data sheet Appendix that I linked in #26 above):

   

The first important detail is that the diode is connected "upside down" (anode to ground), so the Op-Amp inverting input is being pulled (very slightly) below ground by the photo-current. The output of the Op-Amp thus rises above ground and pushes current back through the resistor until it equals the photocurrent (because the Op-Amp has negligible input current and very high voltage gain, so the negative input must also be at almost exactly zero volts).

You may be surprised that the answer to your question about the (voltage) gain is "perhaps a million" (the open loop gain of the Op-Amp), but remember that we are trying to measure the "short-circuit" current from the diode and you don't get much voltage across a short-circuit! The point is that this amplifier is converting a (small) current to a voltage (as does a resistor, of course) in a very predictable manner. The "conversion gain" is given simply by the resistance, for example a 2k resistor would give a 2 volt output for a 1 mA photocurrent (i.e. the "gain" is 2 V/mA).

Therefore, this amplifier is NOT (fundamentally) an "integrator", the capacitor is primarily to stabilise the Op-Amp (i.e. to prevent it oscillating at high frequency because it has a high voltage gain). However, a much larger capacitor value than "necessary" may be used to act as a low pass filter to stabilise (average) the output signal.

(12-06-2015, 17:43)hvalentim Wrote:  This fellow (p. 43) should know what he is talking about:
Harrison, G. (2015) Meteorological Measurements and Instrumentation. Oxford, Wiley-Blackwell.

Yes his circuit is basically the same, I'll let you decide whose design and explanation you prefer. Smile But IMHO (and perhaps Davis') it may be unnecessarily complicated! The key is the Op-Amp: If you use a "Single Rail" Op-Amp, they have a statement such as:

"Input voltage range extends below ground, Output swings rail-to-rail" (AD822),

so it is really not necessary to bias up the inputs if a suitable Op-Amp is chosen. Admittedly the output might not pull completely down to ground (at zero photocurrent), but alternatively, if the inputs are biassed higher than ground, then the bias voltage needs to be measured (or calculated) and subtracted from the Output signal - very probably giving a greater "zero" error than the slight loss of swing (with a grounded input).

Cheers, Alan.
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Messages In This Thread
Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:37
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:38
RE: Measuring Solar Radiation based on Photovoltaic Cells - by fehmi - 04-02-2016, 21:21
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 05-02-2016, 02:46
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:40
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:41
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 07-09-2014, 11:46
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 08-09-2014, 20:30
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 09-09-2014, 11:24
RE: Measuring Solar Radiation based on Photovoltaic Cells - by water01 - 09-09-2014, 00:13
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 09-09-2014, 03:52
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 09-09-2014, 15:13
RE: Measuring Solar Radiation based on Photovoltaic Cells - by water01 - 09-09-2014, 20:17
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 09-09-2014, 22:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by water01 - 09-09-2014, 23:15
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 10-09-2014, 00:45
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 12-01-2015, 13:50
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 14-01-2015, 20:15
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Brett - 13-01-2015, 12:09
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 13-01-2015, 12:42
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Brett - 24-01-2015, 23:09
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 24-01-2015, 23:26
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Brett - 25-01-2015, 08:51
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 25-01-2015, 19:42
RE: Measuring Solar Radiation based on Photovoltaic Cells - by tyntop - 02-02-2015, 23:52
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-02-2015, 03:27
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 01-04-2015, 17:06
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-04-2015, 03:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by strkomis - 29-05-2015, 08:20
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 29-05-2015, 10:52
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 29-05-2015, 18:40
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 02-06-2015, 11:22
ideas to improve the measuring of solar radiation - by hvalentim - 03-06-2015, 11:01
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-06-2015, 11:50
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 03-06-2015, 13:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-06-2015, 17:33
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 05-06-2015, 15:28
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 11-06-2015, 04:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 11-06-2015, 18:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by tyntop - 11-06-2015, 19:26
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 11-06-2015, 19:47
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 11-06-2015, 20:17
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 12-06-2015, 00:44
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 12-06-2015, 06:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 12-06-2015, 13:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 12-06-2015, 17:43
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 13-06-2015, 00:16
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 16-06-2015, 11:08
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 13-06-2015, 01:02
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 13-06-2015, 00:49
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 13-06-2015, 00:56
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 13-06-2015, 11:11
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 14-06-2015, 02:41
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 16-06-2015, 23:53
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 13-06-2015, 14:19
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 16-06-2015, 15:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hvalentim - 16-06-2015, 16:26
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 16-06-2015, 17:26
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 17-06-2015, 02:52
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 30-06-2015, 18:16
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 30-06-2015, 21:28
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 12-07-2015, 11:30
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 12-07-2015, 15:19
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 12-07-2015, 16:43
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 12-07-2015, 23:31
RE: Measuring Solar Radiation based on Photovoltaic Cells - by zitoune - 18-07-2015, 02:40
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 16-07-2015, 14:19
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 18-07-2015, 03:46
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 18-07-2015, 15:32
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-08-2015, 02:47
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 18-07-2015, 15:40
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 18-07-2015, 15:59
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 19-07-2015, 10:26
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 19-07-2015, 17:57
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 20-07-2015, 10:49
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 20-07-2015, 11:07
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 20-07-2015, 11:17
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 21-07-2015, 16:25
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 24-07-2015, 02:38
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 25-07-2015, 15:44
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 02-08-2015, 14:27
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 02-08-2015, 15:42
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 02-08-2015, 17:30
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 03-08-2015, 17:22
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 03-08-2015, 04:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-08-2015, 22:53
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 03-08-2015, 12:38
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 03-08-2015, 13:47
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 08-08-2015, 07:39
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 08-08-2015, 15:21
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 09-08-2015, 14:48
RE: Measuring Solar Radiation based on Photovoltaic Cells - by strada916 - 12-08-2015, 14:23
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 12-08-2015, 14:45
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 12-08-2015, 16:20
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 12-08-2015, 19:07
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 13-08-2015, 09:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 13-08-2015, 15:48
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 19-08-2015, 00:53
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 19-08-2015, 16:51
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 29-08-2015, 04:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by seth22 - 05-09-2015, 09:12
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 06-09-2015, 16:48
RE: Measuring Solar Radiation based on Photovoltaic Cells - by laulau - 22-01-2016, 14:11
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 23-01-2016, 13:51
RE: Measuring Solar Radiation based on Photovoltaic Cells - by laulau - 23-01-2016, 17:39
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllanG - 23-01-2016, 17:56
RE: Measuring Solar Radiation based on Photovoltaic Cells - by laulau - 24-01-2016, 10:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 24-01-2016, 11:05
RE: Measuring Solar Radiation based on Photovoltaic Cells - by laulau - 30-01-2016, 11:13
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 30-01-2016, 21:39
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 12-02-2016, 00:28
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 13-02-2016, 21:10
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 13-02-2016, 22:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 14-02-2016, 00:07
RE: Measuring Solar Radiation based on Photovoltaic Cells - by JT118 - 14-02-2016, 16:25
RE: Measuring Solar Radiation based on Photovoltaic Cells - by meteobreda - 04-04-2016, 16:20
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 07-04-2016, 11:21
RE: Measuring Solar Radiation based on Photovoltaic Cells - by meteobreda - 07-04-2016, 21:15
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 07-04-2016, 22:06
RE: Measuring Solar Radiation based on Photovoltaic Cells - by zitoune - 17-08-2016, 16:36
RE: Measuring Solar Radiation based on Photovoltaic Cells - by zitoune - 18-08-2016, 09:58
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 18-08-2016, 10:52
RE: Measuring Solar Radiation based on Photovoltaic Cells - by zitoune - 18-08-2016, 11:12
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 18-08-2016, 23:29
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 26-06-2017, 20:58
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 27-08-2017, 00:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 27-08-2017, 09:28
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 27-08-2017, 11:01
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 27-08-2017, 20:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 27-08-2017, 00:48
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 27-08-2017, 02:36
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 27-08-2017, 20:04
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 27-08-2017, 23:09
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 27-08-2017, 23:16
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 27-08-2017, 23:28
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 28-08-2017, 00:59
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 28-08-2017, 14:33
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 28-08-2017, 17:25
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 30-08-2017, 02:02
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 31-08-2017, 11:00
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 31-08-2017, 04:36
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 31-08-2017, 15:46
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 31-08-2017, 22:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 01-09-2017, 00:07
RE: Measuring Solar Radiation based on Photovoltaic Cells - by jgveill - 01-12-2017, 20:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by f4aii - 01-12-2017, 07:13
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 01-12-2017, 11:03
RE: Measuring Solar Radiation based on Photovoltaic Cells - by f4aii - 01-12-2017, 13:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 01-12-2017, 21:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 19-07-2019, 14:34
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hornychz - 19-07-2019, 16:11
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 19-07-2019, 16:38
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hornychz - 19-07-2019, 22:36
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 22-07-2019, 12:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 26-07-2019, 10:16
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hornychz - 27-07-2019, 15:01
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 29-07-2019, 11:29
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 26-07-2019, 13:43
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Aggotrom - 26-07-2019, 16:01
RE: Measuring Solar Radiation based on Photovoltaic Cells - by HF_ATL - 18-08-2019, 21:37
RE: Measuring Solar Radiation based on Photovoltaic Cells - by AllyCat - 18-08-2019, 22:56
RE: Measuring Solar Radiation based on Photovoltaic Cells - by uncle_bob - 20-08-2019, 01:14
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 18-08-2019, 22:25
RE: Measuring Solar Radiation based on Photovoltaic Cells - by SSHEEHY - 07-03-2021, 20:27
RE: Measuring Solar Radiation based on Photovoltaic Cells - by hornychz - 08-03-2021, 00:46
RE: Measuring Solar Radiation based on Photovoltaic Cells - by HF_ATL - 18-08-2019, 23:37
RE: Measuring Solar Radiation based on Photovoltaic Cells - by HF_ATL - 20-08-2019, 08:57
RE: Measuring Solar Radiation based on Photovoltaic Cells - by Werk_AG - 08-03-2021, 05:46



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