4.1    Key findings
We have found out that Arduino is a very helpful tool to help us control and program things. It is lightweight, affordable and has numerous applications. We have also learned that the wiring of the different components is very important as one small mistake could lead to malfunction, or worse, a short circuit of the components.

4.2    Evaluation of engineering goals
We have managed to attain the goal of keeping it small and fit it into small box. This makes the pH sensor portable and easy to use. Unfortunately, we could not reach our goal of keeping the production cost low as the pH probe was expensive, due to shipping costs.

4.3   Areas for improvement
During the wiring and connecting of LCD screen and the arduino, we did not use the pH probe for quite a long periods of time which may lead to issues later on as the pH probe would be spoilt because when not the pH probe is not in use, the pH probe must be kept wet all times to avoid the pH sensing membrane dehydration and the subsequent dysfunction of the electrode. It is important that the pH meter should be calibrated before each measurement to ensure that we get accurate pH readings for our measurements. For normal use calibration should be performed once (or every time you restart the device) as calibration data would be stored in the device itself until it is reset. The reason for this is that the glass electrode does not give a reproducible electromotive force(e.m.f.) over longer periods of time. Calibration should be performed with at least two standard buffer solutions that span the range of pH values to be measured. We did not calibrate before each time as we mistakenly believe that this poses as risk to the pH probe. From now onwards we will be calibrated before testing out as we did our research and found out our mistake.

We did not keep the pH probe at a upright position all the times so it might not be wet all the time therefore leading to the possibility that the membrane may be dried up. Thankfully, that did not happen and the pH sensor remained functional. We should also have added more solution so it will be wet even if it slanted and turned rather than counting on luck to keep us safe.

We also keep the arduino on for long periods of time. Therefore,the arduino could have overheated and melted internally due to too much excessive heat and fail to function. Thus, we should have ensured that the pH sensor is always off it when it is not in use.

We also should have rinsed the probe with distilled water or deionized water to remove any traces of the solution being measured, blotted it with a sterile paper towel to absorb any remaining water which could dilute the sample and thus alter the reading leading to inaccurate measurements which we definitely want to avoid at all cause. This would also lead to cross-contamination when we immerse it in another solution as those two solutions may react and cause a change in the pH value rendering it useless (or destroying the sample)

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