1. Done by : 1-Amr Ghaith 2-Abdallah Hassouneh
Universal shunt
Done by :
1-Amr Ghaith
2-Abdallah Hassouneh

2. Universal Shunt Also known as Ayrton Shunt
Ayrton shunt eliminates the possibility of having the meter in the circuit without a shunt
used to increase the range of a galvanometer
Ayrton shunt used with an ammeter consists of several series connected resistors all connected in parallel with PMMC instrument
range change is effected by switch between resistor junction

5. The selector switch S ,selects the appropriate shunt required to change the range of the meter
When the position of the switch is “1”then R1 is in parallel with the series combination of R2,R3 and Rm
When the position of the switch is “2” then R1 and R2 are in parallel with R3 and Rm
shunt

6. Note:
-The larger the current, the value of the shunt resistance may become very small.
-When using an ammeter you have to be aware of the following:
1. Observe the correct polarity.
reversed polarity causes the movement to deflect against the mechanical stop (which cause some damage to the movement).
2. Never connect the ammeter across the element to
be measured.

7. Here, due to the low resistance of the ammeter, this would draw a damaging high current and destroy the movement.
Therefore, an ammeter must always be connected in series with the element to be measured.
3. When use a multi range ammeter first use the high current range, then decrease as required.

8. Design an Ayrton shunt to provide an ammeter with a current range of 0-1 mA, 10 mA, 50 mA and 100 mA. A D’ Arsonval movement with an internal resistance of 100Ω and full scale current of 50 uA is used.
1mA _
D’Arsonval Movement +
10mA
50mA
100mA

9. Rs=R1+R2+R3+R4=(Im)(Rm)/Is Rs=(0.05)(100)/( 0.95)= 5.26 Ω
1-Ampere
Is= I - Im = = 0.95 mA
Rs=R1+R2+R3+R4=(Im)(Rm)/Is
Rs=(0.05)(100)/( 0.95)= 5.26 Ω
R1+R2+R3+R4= 5.26 Ω
1mA _
D’Arsonval Movement +
10mA
50mA
100mA

10. Rs=(R1+R2+R3)=(Rm+R4)(Im)/(Is) R1+R2 +R3 – 0.005R4=0.5
10-milliAmpere
Is= = 9.95mA
Rs=(R1+R2+R3)=(Rm+R4)(Im)/(Is)
R1+R2 +R3 – 0.005R4=0.5
50-milliAmpere
Is= = 49.95mA
Rs=R1+R2=(Rm+R3+R4)(Im)/(Is)
R1+R R =0.1
1mA _
D’Arsonval Movement +
10mA
50mA
100mA

11. 100 milliAmpere Is=100- .05= 99.95mA Rs=R1=(Im)(Rm+R2+R3+R4)/(Is)
R R R3-.005R4=.05
1mA _
D’Arsonval Movement +
10mA
50mA
100mA

12. Ra=0.049
Rb=
Rc=
Note: if we design the circuit in the example as shown in the figure, we will observe the following results: