The processes in a chemical factory are monitored by sensors connected to a microprocessor.

Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

1. [4] 1 mark for appropriate sensor and 1 further mark for appropriate use. Two from: ∞ Gas (sensor) ... e.g. to measure the levels of oxygen/carbon dioxide / nitrogen in the factory to make sure they are not too high / low ∞ Temperature (sensor) ... e.g. to measure the temperature of the chemicals to make sure it is not too high/low ∞ Motion / Infra-red (sensor) ... e.g. to detect any persons in an unauthorised area of the factory ∞ Pressure (sensor) ... e.g. to measure the pressure of chemicals flowing through pipes to check that level are not too high / low ∞ pH (sensor) ... to measure the pH to make sure the acidity / alkalinity of the chemicals is correct ∞ Light (sensor) ... to measure the level of light to make sure it remains at a constant level for the chemical process
2. [5] Five from: ∞ Sensors send signals to microprocessor ∞ Analogue signals are converted to digital (using ADC) ∞ Microprocessor compares value to stored value ... ∞ If out of range / matches stored values ∞ ... signal sent to alert workers (e.g. sound alarm) ∞ ... microprocessor send signal to cause an action to occur e.g. cool a process down, heat a process up, add a chemical ∞ ... no action taken ∞ Output/record readings ∞ Monitoring is continuous