LCX_UserManual_en_08_1.pdf - 第61页

Measurement setups R&S ® LCX Series 61 User Manual 1 179.2260.02 ─ 08 6.3 Configuring BIAS Referred to as biasing defines the method of superimposing a voltage or current on an existing voltage/current to shift the o…

Measurement setups

R&S

LCX Series

60User Manual 1179.2260.02 ─ 08

Depending on a bias required for your measurement, see Section 6.3, "Configuring

BIAS", on page 61 on how to proceed.

Considerations for test signal configuration

●

Dependency of the selected impedance range and the low impedance mea-

surement setting

The impedance range depends on various settings, e..g., the range selection and

the setting of the "LowZ" state.

The following overview explains the corresponding setting (in quotes) for the impe-

dance in the expected range:

LowZ Mode > ON

– ≤10 Ω

"3 Ω": measures values from 0 Ω to ≈3 Ω

– >10 Ω

"10 Ω": measures all values but with limited accuracy

"30 Ω": measures values from 30 Ω up to infinity

LowZ Mode > OFF

– ≤100 Ω

"3 Ω": measures values from 0 Ω to ≈3 Ω

– >100 Ω

"100 Ω": measures all values but with limited accuracy

"300 Ω": measures values from 300 Ω up to infinity

To achieve best measurement results for the expected sample component, select

the range as close to these limits as possible.

Examples for LowZ Mode > OFF, based on the range settings 3 Ω, 10 Ω, 30 Ω,

100 Ω, 300 Ω, 1 kΩ, 3 kΩ, ...:

– 1.2 Ω DUT > select 3 Ω range

– 3.1 Ω DUT > select 10 Ω range

– 150 Ω DUT > select 100 Ω range

– 310 Ω DUT > select 300 Ω range

Auto range

The auto range function selects the range that fits best automatically.

●

Dependency of the mains frequency and the test signal frequency for high

impedances

Measuring high impedances with a signal frequency of ≈100 Hz or 120 Hz lead to

inaccurate readings as the mains frequency with usually 50 Hz / 60 Hz interferes

the test signal frequency.

For an example on how to configure the test signal parameters, see "Setting up the

test signal" on page 35.

Configuring the test signal

Measurement setups

R&S

LCX Series

61User Manual 1179.2260.02 ─ 08

6.3 Configuring BIAS

Referred to as biasing defines the method of superimposing a voltage or current on an

existing voltage/current to shift the operating point of an electronic component to a spe-

cific value.

With the bias function of the R&S LCX, you can predefine a working DC bias that cor-

responds to an expected supply voltage, or (current) in a circuit. The function enables

you to measure the component sample under operating conditions, as expected for the

intended use.

Example: DC dependency of inductors

To measure the current flowing through an inductor under real conditions, e.g., in

power supplies, the current of approximately < 0.1 mA supplied by the R&S LCX is not

sufficient. To achieve higher current, the most common method is to superimpose the

AC with a DC current.

How to: "Setting a current bias" on page 63

Example: DC dependency of capacitors

Some capacitor types, e.g. electrolytic or tantalum capacitors, require a positive volt-

age bias to achieve accurate measurements of the component sample. To add the

bias, you can use either the internal bias source, or supply the bias externally, e.g.

using a power supply.

How to: "Setting an external voltage bias" on page 62

6.3.1 Internal bias voltage

Setting an internal voltage bias

To bias a capacitive component sample:

1. To select the capacitance measurement (DUT component type), press the [C] key.

2. Configure the test signal.

3. To select the parameters for measurement results display:

a) Select the measurement pair softkey in the upper left corner, to open the selec-

tion editor.

b) Select the parameters "Cp-D" (parallel capacitance, dissipation factor).

c) Confirm you selection.

d) Repeat the steps to select the second parameters, e.g. select "Cp-Rp" (parallel

capacitance, parallel resistance).

4. To set the voltage bias value:

a) Press the [Bias Level] key.

b) Enter, e.g. 5 V using the keypad on the screen.

Confirm with

Configuring BIAS

Measurement setups

R&S

LCX Series

62User Manual 1179.2260.02 ─ 08

6. Set up the measurement of the capacitance as described, e.g. in "Measuring a

capacitor" on page 65.

7. To activate the voltage bias, press the [Bias Enable] key.

The lighting [Bias Enable] key indicates that bias is active.

Deactivating current bias

To turn off current bias:

1. Press the [Bias Enable] key.

The unlit [Bias Enable] key indicates that current bias is deactivated.

2. Remove the component sample.

6.3.2 External voltage bias

Option: R&S LCX-K108

The readback voltage indicated on the "GUI" relies on the external power supply that

must be activated. If the power supply output is deactivated or the connection is open,

both, the test signal voltage monitor and the external bias voltage monitor can be inac-

curate.

Setting an external voltage bias

For safety reasons, the instrument limits the test signal level to 2 V when using exter-

nal voltage bias.

To bias a capacitive component sample with a DC voltage supplied by a power supply

instrument:

NOTICE! Check all cables to make sure that they are not damaged.

Connect the safety sockets of the power supply with the cables of the same color

to the corresponding External Voltage Bias at the rear panel.

Note: The voltage at the + bias input must be positive regarding the - bias input.

Do not apply a negative voltage at the bias input.

The output of the power supply must be floating against ground.

NOTICE! Risk of instrument damage.

Too high external voltage bias can damage the circuitry of the instrument.

Do not apply a voltage higher than the specified 40 V DC to the external voltage

bias inputs.

NOTICE! External BIAS requires a constant voltage. Before applying the voltage,

make sure that you have set the constant voltage mode in the supplying instru-

ment. Refer to the user manual of the power supply.

Set the output voltage of the supplying instrument to constant voltage mode.

Configuring BIAS