no faith in coductivity probe

[gino555]

my conductivity probe seems to drift a bit in the downward direction so i have decided to calibrate it for the 2nd time in 2 weeks
i float the liquid in the sump for a hour before calibration, then I test the liquid with the ghl probe and it read 24.6 so started to calibrate my probe and selected
aquarium temp probe> 50ms and 24.6 for the calabration fluid after I save the data i then leave the probe in the solution and it reads less than 49ms,
so then I pour the solution in to a sandwich bag and place the sandwichbag with the liquid in the sump and insert the probe into the liquid and after 30 mins the reading is 49.5ms

am I doing something wrong??????? this is driving me mad

is there any detailed instructions on calibrating the conductivity probe?

[GHL Support]

The most important parameter for the conductivity calibration is the temperature.
Here a more detailed calibration instruction:

3.9.2 Calibration
This function permits the calibration of the conductivity electrode. Only when the ProfiLux aquarium computer has been calibrated for the relevant conductivity electrode can the correct conductivity value be recorded. Calibration is necessary whenever a new electrode is connected. In addition calibration should be repeated from time to time because of possible changes in the actual functioning of the electrode. Please follow the instructions provided by the electrode manufacturer. The electrode should always be carefully dried (with air, by shaking, or with a dry tissue) before immersion in a calibrating solution! First enter the calibration tolerance (between 1 and 3), which forms the basis of the calibration. In the case of old or disturbance-sensitive conductivity electrodes it may happen that the measurement may not be adequately stabilised and calibration is not possible. Depending on the circumstances it may nevertheless be possible to stabilise such electrodes by increasing the calibration tolerance, but naturally at the expense of accuracy of measurement. In principle the calibration process should be performed using the smallest possible calibration tolerance. Thereafter you will have the option of setting the second calibration value within the range 1000 μS to 2000μS (fresh water) or 40mS to 80mS (salt water) (depending on the standard calibration fluid available). Next you must configure whether temperature compensation is to be effected using a fixed temperature setting (Aquarium temp. manual) or a measured value (in which case select the relevant temperature sensor). In the event that Aquarium temp. manual is selected then next enter the relevant temperature. Next enter the temperature of the calibration liquid. Note: The simplest method is to place the (firmly closed) container of calibration liquid in the tank for a while until the temperatures have equalised. Obviously this is feasible only if the aquarium temperature is known. The actual calibration follows next. First you will be asked to hold the electrode in the air (i.e. it shouldn’t be placed in the calibration liquid at this stage). The electrode should already be plugged in! Thereafter pressing RETURN will start the measurement process, during which two numbers will be seen in the lower line of the display. The left-hand number gives the maximum time remaining in seconds. If this time expires without the measurement stabilising sufficiently then the electrode will be deemed defective and the calibration aborted. The right-hand number shows the measurement in an internal code. ProfiLux Plus II recognises automatically when this value has stabilised and then terminates the measurement process. After this measurement you will next be asked to immerse the electrode in the calibration solution (with the previously set calibration value). Again the measurement process is started by RETURN. When this measurement too is completed, you will be asked whether the data are to be stored. If no errors have occurred, confirm with Yes. Finally, it is advisable to check the calibration. First hold the electrode in the air – is the reading around 0μS (fresh water) or 0mS (salt water)? Then connect the electrode and immerse it in the calibration solution. Is a figure approximating to the upper calibration value now displayed?

[gino555]

I have followed the calibration process, I then left the probe in the air and it read 0.1 and the I put the solution back in the sump to make sure it was tank temp, then put the probe back in the solution and it read 50.6
so I re calibrated and put the solution back in the sump for an hour put the probe in the air and it read 0.1 again when I took the solution out of the sump and put the probe in it read 49.2:eek:



could this probe be faulty?


















The most important parameter for the conductivity calibration is the temperature.
Here a more detailed calibration instruction:

3.9.2 Calibration
This function permits the calibration of the conductivity electrode. Only when the ProfiLux aquarium computer has been calibrated for the relevant conductivity electrode can the correct conductivity value be recorded. Calibration is necessary whenever a new electrode is connected. In addition calibration should be repeated from time to time because of possible changes in the actual functioning of the electrode. Please follow the instructions provided by the electrode manufacturer. The electrode should always be carefully dried (with air, by shaking, or with a dry tissue) before immersion in a calibrating solution! First enter the calibration tolerance (between 1 and 3), which forms the basis of the calibration. In the case of old or disturbance-sensitive conductivity electrodes it may happen that the measurement may not be adequately stabilised and calibration is not possible. Depending on the circumstances it may nevertheless be possible to stabilise such electrodes by increasing the calibration tolerance, but naturally at the expense of accuracy of measurement. In principle the calibration process should be performed using the smallest possible calibration tolerance. Thereafter you will have the option of setting the second calibration value within the range 1000 μS to 2000μS (fresh water) or 40mS to 80mS (salt water) (depending on the standard calibration fluid available). Next you must configure whether temperature compensation is to be effected using a fixed temperature setting (Aquarium temp. manual) or a measured value (in which case select the relevant temperature sensor). In the event that Aquarium temp. manual is selected then next enter the relevant temperature. Next enter the temperature of the calibration liquid. Note: The simplest method is to place the (firmly closed) container of calibration liquid in the tank for a while until the temperatures have equalised. Obviously this is feasible only if the aquarium temperature is known. The actual calibration follows next. First you will be asked to hold the electrode in the air (i.e. it shouldn’t be placed in the calibration liquid at this stage). The electrode should already be plugged in! Thereafter pressing RETURN will start the measurement process, during which two numbers will be seen in the lower line of the display. The left-hand number gives the maximum time remaining in seconds. If this time expires without the measurement stabilising sufficiently then the electrode will be deemed defective and the calibration aborted. The right-hand number shows the measurement in an internal code. ProfiLux Plus II recognises automatically when this value has stabilised and then terminates the measurement process. After this measurement you will next be asked to immerse the electrode in the calibration solution (with the previously set calibration value). Again the measurement process is started by RETURN. When this measurement too is completed, you will be asked whether the data are to be stored. If no errors have occurred, confirm with Yes. Finally, it is advisable to check the calibration. First hold the electrode in the air – is the reading around 0μS (fresh water) or 0mS (salt water)? Then connect the electrode and immerse it in the calibration solution. Is a figure approximating to the upper calibration value now displayed?

[GHL Support]

Can you give us the ADC values of the probe, please?

[gino555]

adc 1=19

adc 2 =373

thanks for the quick response:)

[GHL Support]

I have followed the calibration process, I then left the probe in the air and it read 0.1 and the I put the solution back in the sump to make sure it was tank temp, then put the probe back in the solution and it read 50.6
so I re calibrated and put the solution back in the sump for an hour put the probe in the air and it read 0.1 again when I took the solution out of the sump and put the probe in it read 49.2:eek:


Are you sure that the probe is dry while holding the probe into the air?
The 0,1 could be caused by a tiny rest of (salt) water on the probe.
You could also disconnect the probe in that moment in order to achieve exactly 0 in the air.