Hays bridge is an AC bridge circuit that is used to measure the self-inductance of circuits. It is an advanced form of Maxwell bridge and can be used to measure inductance of circuits with higher quality factors (Q>10) compared to Maxwell bridge which is only suitable for coils with Q factors between 1-10. The construction of Hays bridge involves connecting four impedances in a wheatstone bridge configuration. By equating the real and imaginary parts of the balance bridge equation, expressions can be derived for the unknown inductance and quality factor of the coil. Hays bridge provides simple equations to determine inductance and Q factor and is suitable for measurements involving coils with high Q factors.

1. ELECTRONICS INSTRUMENT &
MEASUREMENT
ELECTRONICS 4TH SEMESTER

2. HAY`S BRIDGE
1. यह एक AC ब्रिज होता है |
2. HAY`S BRIDGE सर्कि ट का SELF INDUCTANCE MEASURE
करने के काम आता है |
3. यह ब्रिज MAXWELL ब्रिज की ADVANCE फॉमि होता है |
4. मैक्सवेल ब्रिज के वल मध्यम Q फै क्टर (1 <Q>10) के इंडक्टर
के INDUCTANCE MEASURE करने के काम आता है जबर्क
HAY`S ब्रिज उच्च Q फै क्टर (Q>10) के सर्कि ट के सेल्फ
INDUCTANCE MEASURE करने के काम आता है |

3. CONSTRUCTION OF HAY`S BRIDGE

4. Z1 = R1 + (1/jwC1)
Z2 = R2
Z3 = R3
Z4 = Rx + jwLx
For Balance bridge , Z1 Z4 = Z2 Z3
So, (R1 + (1/jwC1))(Rx + jwLx) = R2 R3
(R1 Rx + Lx/C1) + j (w Lx R1 – Rx/w C1) = R2 R3
REAL & IMAGINARY PART COMPARE करने पर
R1 Rx + Lx/C1 = R2 R3 --------- (b)
wLx R1 – Rx / w C1 = 0
wLx R1 = Rx / w C1

5. Rx = w2 Lx C1 R1 -----(a)
समीकरण a का मान समीकरण b में रखने पर एवं
दोनों को हल करने पर
Lx = R2R3C1/(1+ ω2R1 2 C1 2)
Rx= ω2C1 2R2R3R1/ω2R1 2C1 2
The Q Facor of the coil is
Q = ωLx/Rx = 1/ ω2R1C1

6. Advantages
The advantages of hays bridge are
1. This bridge is used for the unknown
inductances to provide a simple expression. It is
appropriate for the coil that has a high Q factor
than the 10 ohms.
2.For the Q factor, this bridge provides a simple
equation.
3.It uses a small resistance value to determine the
quality factor.

7. Disadvantages
• The disadvantages of hays bridge are
• It is not applicable for the measurement of the
coil which has less than 10 ohms Q factor.
• The balanced equation of the bridge depends on
operating frequency and thus the frequency
change will influence the measurements.
• The Q factor is used to determine the main
relationship between the energy which is stored
& dissipated within the circuit.

8. Applications of Hays Bridge
• The applications are
• This bridge is used to determine the self-
inductance of the circuit.
• This is used to overcome the drawback of
Maxwell’s bridge. The
• This bridge circuit is used to measure the high
QF (quality factor) in the circuit.