LCR Meter vs LCR or Bridge
- Thread starter Liam1980
- Start date
KeithWalker
- Joined Jul 10, 2017
- 2,702
If you don't know what the difference is, then I recommend that you look up on the internet what they are and how they work. The information is all there waiting for you. Once you understand what they are, the advantages and disadvantages will become apparent to you.
DickCappels
- Joined Aug 21, 2008
- 9,607
If you want to have precise control over the excitation signal, want plenty or resolution, and don't mind fiddling with dials to get to the answer then a manual bridge would give the best performance. I used to use a bridge but found it very slow going and now rely on LCR and L meters.
Bridge measurements refer to a circuit configuration based on the Wheatstone bridge.
In a classic bridge measurement, R1 and R3 in the circuit above are known and fixed resistors. Rx is the unknown resistor.
R2 is adjusted until the galvanometer VG reads zero voltage and current. This meter is usually a very sensitive 50μA moving coil ammeter. The measurement does not depend on the supply voltage. It also does not require the ammeter to be calibrated.
For capacitance and inductance measurements, the DC supply is replaced with an AC source.
An LCR meter might use other forms of AC techniques that measure reactance.
In a classic bridge measurement, R1 and R3 in the circuit above are known and fixed resistors. Rx is the unknown resistor.
R2 is adjusted until the galvanometer VG reads zero voltage and current. This meter is usually a very sensitive 50μA moving coil ammeter. The measurement does not depend on the supply voltage. It also does not require the ammeter to be calibrated.
For capacitance and inductance measurements, the DC supply is replaced with an AC source.
An LCR meter might use other forms of AC techniques that measure reactance.
KeithWalker
- Joined Jul 10, 2017
- 2,702
Is this a homework question? If so, we need to see your best effort at a response before we can help.
I must say right away that the LCR meter must operate at different frequencies.
DickCappels
- Joined Aug 21, 2008
- 9,607
what is an "LCR"?
I have an LR meter that uses a 1 kHz sine wave and looks at the magnitude of the voltage signal across the reactive component by measuring the current over a sampling signal in phase with the 1 kHz current source and then again with a 90° (quarter cycle) delay. This allows calculation of the real (resistive) and imaginary (inductive) induced voltage and from that the resistance and inductance.
There are others that resonate, for example, an unknown L against a known C in an oscillator and use the measured resonant frequency of the combination of the unknown and known reactive components to calculate the value of the unknown reactive component.
And an RF inductance meter that injects fixed frequency pulses into an inductor, and after low pass filtering provides a voltage proportional to the inductance.
I have an LR meter that uses a 1 kHz sine wave and looks at the magnitude of the voltage signal across the reactive component by measuring the current over a sampling signal in phase with the 1 kHz current source and then again with a 90° (quarter cycle) delay. This allows calculation of the real (resistive) and imaginary (inductive) induced voltage and from that the resistance and inductance.
There are others that resonate, for example, an unknown L against a known C in an oscillator and use the measured resonant frequency of the combination of the unknown and known reactive components to calculate the value of the unknown reactive component.
And an RF inductance meter that injects fixed frequency pulses into an inductor, and after low pass filtering provides a voltage proportional to the inductance.
Exactly what are your needs ?
Precise or indicative measurements ?
What are you measuring, R, C, or L?
What is the range of values?
For precise measurements, use a bridge method.
Are you doing a one time measurement or are you looking for a lab bench instrument?
What are your requirements for resolution and accuracy?
Do you need NIST traceable certification?
Then you'll also need a fixture for SMD work and maybe a 4 wire Kelvin clip set also.
If you're serious about this stuff some study here would be advised:
https://www.eevblog.com/forum/testgear/cheap-smd-lcr-fixture-the-good-bad-and-ugly!/
How precise? Numbers?
For example - MS5308 Mastech autorange digital bridge LCR meter:
Link: MS5308 user's manual
They can all be the same and have just one function, to make L, C and R measurements.
Pick the type that suits your accuracy needs, form factor you require and your budget.
I went through this 20 years ago and selected top quality SMD smart tweezers that have outlasted several DMM's and they are the first tool out when testing/measuring any component.
In three sentences:
LCR Meter: it is LCR Meter, method of measuring is not described.
LCR: it is LCR Meter, only name is shorted for convenience, method of measuring is not described.
Bridge: it is LCR Bridge Meter, where "Bridge" describes method of measuring and name is shorted for convenience.
KeithWalker
- Joined Jul 10, 2017
- 2,702
I already answered your question in post #2.
RE:""Liam1980 said:
i need a very very Precise measurements""
Then You need nor the bridge, nor the measurer, but the Network Analyser (VNA). All other methods are deviated by parasythic L and R, whilst the VNA is solely method accurately measuring all the three in one push. Indicative accuracy - measurer +/- 2 pF 10 uH 1 Ohm. Bridge 0.5 pF 0.1 uH 0.1 Ohm. VNA +/- 0.01 pF 0.1 nH 0.0001 Ohm.
Indicative about speed: Meter about 10 kHz, bridge about 100 Hz to 1 kHz, VNA 50 kHz to 10 GHz if You want see as the diagram. Or set the fixed value in this range.
i need a very very Precise measurements""
Then You need nor the bridge, nor the measurer, but the Network Analyser (VNA). All other methods are deviated by parasythic L and R, whilst the VNA is solely method accurately measuring all the three in one push. Indicative accuracy - measurer +/- 2 pF 10 uH 1 Ohm. Bridge 0.5 pF 0.1 uH 0.1 Ohm. VNA +/- 0.01 pF 0.1 nH 0.0001 Ohm.
Indicative about speed: Meter about 10 kHz, bridge about 100 Hz to 1 kHz, VNA 50 kHz to 10 GHz if You want see as the diagram. Or set the fixed value in this range.
