motor controls 3 lesson 2
If an analog circuit with a 4-20 mA DC-current-based analog signal is reading 12 mA and a 1-5 VDC relay is connected to the circuit with a 250 ohm resistor in parallel with the input terminals, what would be the relay input voltage?
3 V DC Note: .012 (I) x 250 (R) = 3 VDC signal
A certain process control system utilizes a tank that is 10 feet tall. The transducer that measures the level of liquid in the tank is located 2 feet from the bottom of the tank. If a 1-5 VDC signal is used to monitor the top 8 feet of water in the tank, how much water is in the tank when the analog value read at the transducer is 3.5 VDC?
7 Note: A 4 volt signal (5 V - 1 V) represents 8 feet of water in the tank. 4 V/8 feet = 0.5 volts per foot. 3.5 volts represents 3.5 V - 1 V = 2.5 volts of signal. 2.5 V/0.5 V = 5 feet of water. Since the transducer is only monitoring the top 8 feet of water in the tank, the height of water in the tank is 2 feet (not monitored) + 5 feet (the measured value) = 7 feet. There are 7 feet of water in the tank.
0-10 VDC, 4-20 ma, and 3-15 psi are examples of what type of signal?
Analog
? signals provide a continuous indication of the value or position of the variable or entity being monitored.
Analog
What type of signal is continuous, varying from a minimum to a maximum value?
Analog
When analog control devices are located large distances from each other, which type of signal is preferable for installing the control wiring?
Current
What type of signal has only two states: ON and OFF?
Discrete
What type of device has one type of analog signal as an input, and produces another type of analog signal as an output?
Signal converter
A 1-5 VDC analog device can be used in a 4-20 mA DC loop circuit if a 250 ohm resistor is connected across the input to the device and the 4-20 mA DC current is routed through the resistor. The current signal produces the proper voltage to operate the 1-5 VDC device.
True
A(n) ? signal can be used to control the speed of a motor, determine the position of a valve, or indicate the level of a tank at every level as the tank fills or empties.
analog
Generally, ? signals with a very low source resistance are less sensitive to electrical noise from welders and electric motor starters.
current
A limit switch is an example of a(n) ? signal.
discrete
Analog devices connected using a voltage type analog signal are connected in ? with each other.
parallel
Analog devices connected using a current loop analog signal are connected in ? with each other.
series
A(n) ? converts from one analog signal range to a different analog signal range when the analog signal values do not match.
signal conditioner
Which type of analog signal can be used to not only control the speed of a motor, but also the direction of rotation of the motor?
±5 VDC
