Ionic sensor calibration - incosistent been 8+ hours

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Sun May 27, 2018 5:22 pm

Cl, Na, NH4,NO3

Been calibrating for 8+ hours getting readings that do not match the calibration mediums.

Questions
1. Is there a required distance between the reference probe and the other probes
2. Although the temperature probe is required, I don't see the temperature value being used in the calls to the methods that do the calibration:

// Calibrate the NO3 sensor
NO3Sensor.setCalibrationPoints(voltages_NO3, NO3concentrations, NUM_POINTS);
// Calibrate the NH4 sensor
NH4Sensor.setCalibrationPoints(voltages_NH4, NH4concentrations, NUM_POINTS);
// Calibrate the Na sensor
NaSensor.setCalibrationPoints(voltages_Na, Naconcentrations, NUM_POINTS);
// Calibrate the Cl sensor
ClSensor.setCalibrationPoints(voltages_Cl, Clconcentrations, NUM_POINTS);

Unlike say my pH probe

// Configure the calibration values for pH
pHSensor.setCalibrationPoints(cal_point_10, cal_point_7, cal_point_4, cal_temp);

Should temperature not be taken into consideration when measuring these Ions? Am I missing some configuration

3. What its the average time (in hours) it should take to calibrate a new N03 probe, I realize time may vary which is why I am asking for an average, i.e. 2 hrs, 2 days, 2 weeks...

Thanks
Jess

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by libelium-dev » Mon May 28, 2018 9:23 am

Hi,

There isn't a required distance between the reference probe and the sensors although we recommend about 20 cm.

The temperature sensor isn't required for ions sensors but it is mandatory when reading the pH sensor.

When the ions sensor are new or they aren't not used for a long time we recommend keep the sensor into its higher calibration solution for a day.

Could you share with us the output through the serial monitor in order to see how the values vary?

Regards

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Mon May 28, 2018 5:28 pm

Thank you a few more questions

1. What about the distance between the individual probes? How far should the Na probe be from the Cl probe to ensure there is no interference when we are calibrating?

2. Can I purchase the new PRO sensors and will they work with my V1.2 Waspmote
3. Can I mix and match the old and PRO sensors, meaning can I use an old Cl sensor with ammoinium PRO sensor?

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Tue May 29, 2018 3:36 am

It would be REALLY helpful if you guys would upgrade your forum to a platform that would support pasting in images. Please..

This Cl- probe has been sitting in calibration medium all day. The voltage has regulated to a consistent 3.637 and should be returning a concentration of 750 as specified on the bottle #3 of the Libelium Calibration Medium.

We are calibrating ONE probe at a time (as you can see) to be sure there is no interference.

Other probes are behaving the same way, the voltage settles out but the concentrations displayed do not match the concentrations on the calibration medium bottle.

Do you have customers that have these ionic probes working in the field and returning accurate values? We are losing confidence here. We expected many hours for the voltage readings to settle, but once they have the concentrations need to reflect what is in the calibration medium to show they are actually working. This is not happening, are other people using the ionic probes successfully?

Thanks
Jess

Temp: 23.4739990234 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=3.0679931640
NH4+: 0.0004873188 ppm/mg*L-1 | - NH4Volts=2.4201874732
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0029949998
Cl-: 2106.0393066406 ppm/mg*L-1 | - ClVolts=3.6375935077
Battery: 44 %
Temp: 23.4048156738 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=2.9921844482
NH4+: 0.0000135766 ppm/mg*L-1 | - NH4Volts=2.1009583473
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0030568747
Cl-: 2095.4367675781 ppm/mg*L-1 | - ClVolts=3.6378405094
Battery: 44 %
Temp: 23.4571533203 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=2.9321487426
NH4+: 0.0000009081 ppm/mg*L-1 | - NH4Volts=1.8598125457
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0029931249
Cl-: 2103.3317871093 ppm/mg*L-1 | - ClVolts=3.6376564502
Battery: 44 %
Temp: 23.3876953125 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=2.4616186618
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.1602775001
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0024999997
Cl-: 2107.6198730468 ppm/mg*L-1 | - ClVolts=3.6375567913
Battery: 38 %
Temp: 23.4222106933 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=2.1380975246
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0029918746
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0019175000
Cl-: 2104.6850585937 ppm/mg*L-1 | - ClVolts=3.6376249790

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by libelium-dev » Tue May 29, 2018 9:20 am

Hi,

There isn't a required distance between the sensors but we recommend calibrate the sensor one per one.

New ions sensors for v15 are compatible with P&S Ions PRO v12.

About calibration process, you have to check that the voltage values are stables but the concentration may not be the one indicated on the boat.

What calibration points did you set in your code? In which calibration solution were immerse the sensors for the shared values. It seems that the voltage for Na+ sensor is incorrect, the voltage value should be higher.

Regards

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Tue May 29, 2018 11:12 pm

You are correct the voltage for Na (and all sensors) displayed is incorrect as they are not in the solution. We are doing one at a time so the only one that we are calibrating now is Cl, only Cl is in the solution.

Questions

1. The voltage for the Cl probe has settled at 3.69 but the concentration as on the bottle should be 750, it is not it is as you can see it just over 1000. Can you please explain this?

2. Are you sure "New ions sensors for v15 are compatible with P&S Ions PRO v12."? I think the sales catalog says different.

3. I understand when the voltage is settled we are getting a consistent reading regarding the electrons, but how does that convert to the concentration of the Ions? We don't specify anywhere in the code what the specific Ion is, the call to ClSensor.calculateConcentration(ClVolts) simply takes voltage and Clsensor is just of type IonSensorClass. In short I am wondering if calculateConcentration() does not have all the information it needs to do the calculation? Does it need to know the type of ion?

Thanks (reading from serial port below)

Battery: 44 %
Temp: 26.6914978027 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=0.0026875000 // probe off
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0019375000 // probe off
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0017787499 // probe off
Cl-: 1121.4802246093 ppm/mg*L-1 | - ClVolts=3.6909687519 // THIS IS THE ONE WE ARE CALIBRATING, 750 is concentration on bottle
Battery: 43 %
Temp: 26.6570434570 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=0.0027443747
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0019090623
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0017512500
Cl-: 1143.0994873046 ppm/mg*L-1 | - ClVolts=3.6902186870
Battery: 43 %
Temp: 26.6570434570 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=0.0028062498
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0017500000
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0016237498
Cl-: 1132.3074951171 ppm/mg*L-1 | - ClVolts=3.6905913352
Battery: 43 %
Temp: 26.6748962402 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=0.0028409376
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0020965623
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0016862499
Cl-: 1134.0611572265 ppm/mg*L-1 | - ClVolts=3.6905305385
Battery: 46 %
Temp: 26.7098083496 Celsius degrees
NO3-: 0.0000000000 ppm/mg*L-1 | - NO3Volts=0.0030340623
NH4+: 0.0000000000 ppm/mg*L-1 | - NH4Volts=0.0020062499
Na+: 0.0000000000 ppm/mg*L-1 | - NaVolts=0.0016893750
Cl-: 1130.4393310546 ppm/mg*L-1 | - ClVolts=3.6906561851

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by libelium-dev » Wed May 30, 2018 9:38 am

Hi,
1. The voltage for the Cl probe has settled at 3.69 but the concentration as on the bottle should be 750, it is not it is as you can see it just over 1000. Can you please explain this?
Did you set the voltage in the code and then upload the code to the node again? The concentration should be close to the calibration solution when you set the calibration points in the code. Make sure the voltage is stable after set it in the code.
2. Are you sure "New ions sensors for v15 are compatible with P&S Ions PRO v12."? I think the sales catalog says different.
Ions Sensors PRO v15 are compatible with Ions Sensors PRO v12.

Code: Select all

3. I understand when the voltage is settled we are getting a consistent reading regarding the electrons, but how does that convert to the concentration of the Ions? We don't specify anywhere in the code what the specific Ion is, the call to ClSensor.calculateConcentration(ClVolts) simply takes voltage and Clsensor is just of type IonSensorClass. In short I am wondering if calculateConcentration() does not have all the information it needs to do the calculation? Does it need to know the type of ion?
Just the voltage and the previously configured calibration points are necessary to calculate the concentration. A approximation line is create with the calibration points and then the voltage values are converted to concentration using the approximation volts/ppm created with the calibration points.

Regards

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Wed May 30, 2018 10:53 pm

yes we are putting the voltage in the code AFTER it has settled - we are going on 4 days of no luck. I have ordered more calibration medium (expensive $500). If this does not resolve the issue how do we trouble shoot this?

I will let this configuration run over the next 5 hours (it is 5:00PM EST Boston MA) and will send you the results at 10:00PM EST. Along with the calibration code

1. Probe Cl
2. Calibration Medium 3 expected concentration 750

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by libelium-dev » Thu May 31, 2018 9:38 am

Hi,

When did you purchase the sensors? Keep in mind that the life expected for this sensor is around 6 months. Even in perfect conditions and low usage the chemical reactions that take place in the reference electrodes will stop working.

Regards

JessieP
Posts: 90
Joined: Fri May 27, 2016 2:39 pm

Re: Ionic sensor calibration - incosistent been 8+ hours

Post by JessieP » Fri Jun 01, 2018 2:01 pm

We purchased them a year ago but they have been sitting in a box up to a few months ago. Each sensor is about $500 USD so this is very disappointing as we spent almost $3K on this (including the reference probe).

I understand if perhaps one sensor was not working but all four are not able to hold a steady reading.

Do you have others customers that have had success with these ion selective probes? This is going on 4-5 days

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