Electronic Troubleshooting
ET 198B
Quiz 4
1. Given the circuit to the right, the X-input gate that
feeds line b3 is output state of High and the W-input
gate that feeds line b3 is output state of Low. What
logic level will be on line b3?
Logic Low
2. What are the three output states of the Tristate
Inverters or buffers?
High (logic 1), Low(logic 0), High impedance on
the output
3. Given the “1of 8” decoder to the right and the logic level
inputs of A=0, B=1, C=1, and Pins 2&14= 0. What are the
logic levels on the output pins?
All output pins except pin 5 will be at a logic level of 1,
pin 5 will be a logic level of 0.
4. Suppose the inductance of the positive power supply foil is 1.75µH. What
would the voltage drop be if the current through it changes by 40 mA in 25ns.
ࢂࡸ = ࡸ
ࢊ࢏
૝૙࢓ ࡭
= ૚. ૠ૞࢓ ࡴ
= ૛. ૡࢂ
ࢊ࢚
૛૞࢔࢙
5. Given a type J thermocouple
junction that is heated to 400C
and the cold ends are at 00C.
What is the thermocouple
voltage?
ࢂ = ࢙࢞ ∆ࢀ = ૞૚
ࣆࢂ
࢞ ૝૙°࡯ = ૛. ૙૝࢓ ࢂ
°࡯
6. Given a platinum temperature sensor resistance = 55 ohms at 00C. What is it’s
resistance at 400C?
ࡾ = ࡾ ࡻ (૚ + ࢻ ∆ࢀ) = ૞૞ષ ( ૚ + ૙. ૙૙૜ૡ૞ ࢞ ૝૙℃) = ૟૜. ૝ૠષ
7. ( T or F ) The resistance of a photoconductive cell (photoresistor) decreases as
the amount of light striking it increases.
8. Given the circuit to
the right and proper
calibration. What
condition will cause
the sonic alarm to
sound?
Something
obstructs the light
striking the photo-resistor
9. Given a 250Ω strain gage with a gage factor of 2 which is mounted to a metal
bar 0.6m long. The bar is stretched under a tension force and the resistance
changes to 251.4 Ω. What is the length of the bar?
R  R0 (1 
L
L
 GF )  251.4(1 
 2)
L
0 .6 m
ઢࡸ =
૙.૟(૛૞૚.૝ି૛૞૙)
૛૞૙ ࢞ ૛
= ૚. ૟ૡ࢓ ࢓
10. Given a 4-20mA current loop used to measure pressures ranging from 0-60 psi.
What pressure does 12mA represent?
60psi/16mA = 3.75psi/mA =>> (12mA-4mA )x 3.75psi/mA = 30psi
11. Math the symbol or equivalent circuit to the device name.
a. DIAC
b. TRIAC
c. SCR
12. ( T or F ) Per the textbook Solid State Relays only use reed relays inside, never
opto-couplers.
13. Given the circuit to the right and the given
120Vrms input signal draw the voltage drop
across the lamp when the coil energizes and
the reed relay closes.
14. Given the circuit to the right, S1 closed,
and the VB voltage and DIAC trigger pulses
for two different settings of the dimmer pot,
draw the load voltage waveforms.
15. ( T or F ) When switching inductive loads with SCRs or TRIACs Kickback
voltages cannot activate SCRs only TRIACs