What Miss Rae's 4th Year Tech Studies Class get up to
Friday, 11 March 2011
Today's Mini Test
Here is today's mini test which will help us prepare for the NAB. You also have to be able to describe the three types of control: On/Off, Continuous and Sequential in relation to a given example.
1. a) The electric shower uses closed loop control (you know that this must be true because you can see the feedback loop - the output is constantly monitored and a change in the input - temperature sensor - leads directly to a change in the output - this will mean that the temperature will remain as constant as possible.)
b) Component X is an error detector. It compares the actual temperature of the shower with the set/desired (or reference) level.
c) The desired temperature is set using the thermostat on the shower. The error detector compares this set input to the actual temperature of the shower sensed by the temperature sensor. Any difference between the two is seen as an error and this signal is sent to the control which then tries to reduce the error by switching the heating element (driven by the transducer driver) either on if it is too cold, or off if it is too warm. This system tries to keep the temperature as constant as possible.
2. The warning light uses open loop control The heating system uses closed loop control
(it is very hard to draw system diagrams in a comment box!)
Warning light:
Cold > Temperature sensor > control > TD > lamp > light
Cold and light are "real life" input/output. They should not be in a box, all the parts of the system should be in boxes with a system boundary around that.
Heating System is too hard to draw here, if you would like the answer again, please come and see me.
Here are the answers:
ReplyDelete1. a) The electric shower uses closed loop control (you know that this must be true because you can see the feedback loop - the output is constantly monitored and a change in the input - temperature sensor - leads directly to a change in the output - this will mean that the temperature will remain as constant as possible.)
b) Component X is an error detector. It compares the actual temperature of the shower with the set/desired (or reference) level.
c) The desired temperature is set using the thermostat on the shower. The error detector compares this set input to the actual temperature of the shower sensed by the temperature sensor. Any difference between the two is seen as an error and this signal is sent to the control which then tries to reduce the error by switching the heating element (driven by the transducer driver) either on if it is too cold, or off if it is too warm. This system tries to keep the temperature as constant as possible.
2. The warning light uses open loop control
The heating system uses closed loop control
(it is very hard to draw system diagrams in a comment box!)
Warning light:
Cold > Temperature sensor > control > TD > lamp > light
Cold and light are "real life" input/output. They should not be in a box, all the parts of the system should be in boxes with a system boundary around that.
Heating System is too hard to draw here, if you would like the answer again, please come and see me.