The salinity sensor in the fish tank system, which we used during the Week 11 ex

Question

The salinity sensor in the fish tank system, which we used during the Week 11 experiment, reads 0.1 % saline, but the fish tank salinity should not exceed 0.071% saline. Assuming the fish tank system holds 279 mL water and that the DI solenoid valve has a flow rate of 5.4 mL/s, how long should the DI solenoid value be powered open (digitalWrite(diPin, HIGH);) to bring the fish tank salinity to the 0.071% salinity limit? Units are in milliseconds to match the delay function used in the MPIDE program; do not include units in your answer. Give your answer to zero decimal places.

Explanation / Answer

Given in question:

Flow rate of valve: 5.4 ml/s

Salinity of water: 0.1%

Required salinity: 0.071%

Total volume of water in tank: 279 ml

From the data we can calculate the concentration of salt present in water i.e. 0.1% which means 0.1 g in 100 ml so it will be 0.279 g in 279 ml or 279mg in 279 ml which can be represent as 1mg/ml

The required concentration of salt in tank is 0.071% which mean 198 mg in 279 ml of water.

Excess salt concentration = 279 – 198

                                              = 81mg

The flow rate of valve is 5.4 ml/s which means it can exchanfe 5.4 ml water (i.e. 5.4 mg salt) in 1 sec.

So tatl required time = (1/5.4) x 81

                                       = 15 sec

So the valve should be opened for 15 seconds.

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