Photo Sensor for colorimeter

Hello,

Please help to find sensor for calorimeter. I am using BPW21 ,But it not give result. My wavelength range is 400 to 670 nm .

Thank you

you can try the chip named TCS230 PROGRAMMABLE COLOR LIGHT-TO-FREQUENCY CONVERTER from TAOSINC
and its new versions
datasheets here : http://www.taosinc.com/Productfamily.aspx?id=5&SD=cs

Share with us your detailed user/application stories. It looks like some sort of IR energy detection?

Sir,
Thank you for this. But please tell that BPW21 is useful for such application and is any way to calibrate the BPW21.
In my project I try to calibrate the BPW21 for concentration in following step
1. I make the red color solution for of different cons. first is 85% and second one is 54% (Both are of accurate value because i cross check it with spectrophotometer meter)
2. I use tungsten bulb of 5V 300mA and a red glass filter of 670nm.
3. Then I put both solution in front of light source one by one
4. But the output voltage and current of BPW21 is nearly same. It not give correct result for change in intensity of light for both solution .Here correct result in form of voltage or current(I try to measure both)

I think i doing something wrong please tell me some way to calibrate the O/P of BPW21

As a first step, I would need more information about the two standard solutions you prepared in order to calculate what the predicted absorbance would be. A dye solution made to be "85%" (wt/wt or wt/vol) would be extremely concentrated. I don't think that is what you meant.

What dye you are using (chemical name)? Can you post its absorption spectrum? What are the concentrations of the dye in molar or any other conventional units? How long is the light path through the dye?

For clarification, does your "red" filter pass 670 nm or absorb at 670 nm?

John

Sir,
I use KMnO4 WITH WATER.And I have a spectrophotometer to test the transmission and absorption . And my red filter pass 670 nm. I send you the arrangement I am using **broken link removed****broken link removed**. Please note that i am using a tungsten light bulb of 5 V and 300mA as light source. And light path is 1.3cm nearly.And full body is painted black. Image give to a idea about the setup. And i use DPM to measure voltage.
Thank you

1. I make the red color solution for of different cons. first is 85% and second one is 54% (Both are of accurate value because i cross check it with spectrophotometer meter)

Click to expand...

One explanation for the results you are getting is that the concentrations of permanganate are way too high. The following calculations are meant as an example to illustrate that point.

We still don't know the actual concentration of permanganate in your solutions. On a weight/weight basis, the concentrations that you mention are impossible. The solubility of potassium permanganate in water is only about 6.8 g/100 mL, which equates to about 0.4M (moles/liter).

The molar absorbance of permanganate at 670 nm is approximately 129 (estimated from this source: https://media.rsc.org/Modern chemical techniques/MCT4 UV and visible spec.pdf ). Thus, a 0.4 M solution would have an absorbance (optical density) in your test system = 129 x 0.4 x 1.3 = 67 = log (Io/I)

In other words, almost no light is getting through that solution. Halving the concentration doesn't help, because you still don't have enough light to detect.

For best results, you want your solutions to have absorbances (optical density) of about 0.1 to 1.0

Another explanation for your results is called "stray light," which means your detector is responding mostly to light that has not passed through the sample.

Suggestions:
1) Make your solutions up to produce absorbances in the range just given. Give that concentration in molar units.
2) Please explain what you mean by this,"And full body is painted black?"
3) Does your detector respond if you wave you hand in front of it?

John

Sir,

As i told you that i cross check it by spectrometer. And "Fully painted black" mean ,I using a plastic stand for glass test tube same as show in fig, and this is painted black. And detector respond for light.
Some important point I want to tell you
1. Detector respond to light
2. It respond to light.I put a water in test tube and take reading it is nearly 300mv(on 670nm) and then I put sample of 85% T in front of it and it give the reading of 312mV and then I calculate the T%. which give the result of 96% which is wrong.

One think I want to know that the BPW21 is suitable for such application ???. I study the basic's of calorimeters and in book it is written that characteristic of sensor used for such type of application must match with human eye pattern. that's why I use BPW21.


Thank you

It would be useful to see your circuit. A photodiode will give a current which is proportional to light when zero or reverse biased but if you are running in photovoltaic mode that won't be the case. You could check the linearity of your measuring system with some neutral density filters.

Keith

I am using DPM for voltage measurement and for current please see the attachment.

You are using the photodiode in photovoltaic mode. You need to be using a transimpedance amplifier to measure the current from the photodiode.

Keith