BCS-10 balanced current source module

This module provides programmable currents from 1 pA to 100 mA with a ±10 V maximum compliance output from DC to 100 kHz sinusoidal output. Derived from Lake Shore’s industry-leading Model 372 AC resistance bridge, the BCS-10 employs a differential or balanced design that helps reduce or eliminate ground loops often encountered in cryostats and other research apparatus. It expands on Model 372 balanced source capability, adding variable frequency and amplitude programmability for enhanced flexibility while maintaining excellent noise performance.

The inclusion of a virtual center-point ground connection further enhances noise performance by allowing the user to determine optimal center-point tie points within given apparatus or equipment setups. The BCS-10 is designed to be paired with the VM-10 module, which provides both single-ended and differential (balanced) input connection and modes. The true differential (balanced) wiring configuration minimizes noise coupled from the environment, such as from power lines, lighting, motors, and other lab equipment.

A typical application of the balanced current source involves low-resistance measurements, where the resistance of the wires connecting the current source to a sensor may be significant. Any imbalance in lead wire resistance results in a common-mode voltage that complicates the measurement of the desired parameter, the voltage across the sensor. The external CMR feature is unique in that it allows the BCS-10 to force some remote node (such as a VM-10 input) to circuit common potential and thus mitigate the effect of unbalanced lead wire resistance.

BCS-10 specifications

Specifications subject to change

Ranges: 100 mA, 10 mA, 1 mA, 100 μA, 10 μA, 1 μA, 100 nA, 10 nA; automatic selection

Compliance: 20 V differential, 10 V single-ended (non-settable)

Maximum power: 1 W, 4-quadrant operation

CMR modes: Off, internal, external

Coupling: DC or AC (1 Hz)

Guard drive: Enable or disable

Rise time: <25 µs, 10% to 90%, zero to full scale, <1 Ω impedance load, 1 µA and above ranges

Settle time: <60 µs to 0.1% of final value, zero to full scale, <1 Ω impedance load, 1 µA and above ranges

Load impedance: Stability maintained with reactive loads up to 50 µF or 1 mH (with 100 Ω damping)

Magnetic field exposure: Operational up to 11 mT DC

Size: 142 mm W × 39 mm H × 89 mm D (5.6 in × 1.5 in × 3.5 in)

BCS-10 module options

Options for the BCS-10 module that you can set on the M81 instrument screen


RangeBandwidth (typical)DC1
±(% rdg + A)
±% rdg + A
Temperature coefficient1,2
±(ppm rdg/°C + A/°C)
Settable resolution
Maximum frequencyFull accuracy maximum frequency
100 mA100 kHz1 kHz0.03% + 5 µA0.15% + 500 nA2 ppm/°C + 100 nA/°C1 µA
10 mA100 kHz1 kHz0.03% + 500 nA0.15% + 50 nA2  ppm/°C + 10 nA/°C100 nA
1 mA100 kHz1 kHz0.03% + 50 nA0.15% + 5 nA2 ppm/°C + 500 pA/°C10 nA
100 µA100 kHz1 kHz0.03% + 5 nA0.15% + 500 pA2 ppm/°C + 200 pA/°C1 nA
10 µA100 kHz1 kHz0.03% + 1 nA0.15% + 50 pA2 ppm/°C + 10 pA/°C100 pA
1 µA10 kHz1 kHz0.5% + 120 pA0.5% + 5 pA5 ppm/°C + 2 pA/°C10  pA
100 nA1 kHz100 Hz0.5% + 60 pA0.5% + 500 fA5 ppm/°C + 2 pA/°C1 pA
10 nA100 Hz30 Hz0.5% + 30 pA0.5% + 50 fA5 ppm/°C + 2 pA/°C100 fA

Noise (typical)

RangeNoise densityNoise at 0.1 Hz to 10 Hz
100 mA1.2 nA/√Hz at 1 kHz10 nA RMS (50 nA p-p)
10 mA200 pA/√Hz at 1 kHz2 nA RMS (10 nA p-p)
1 mA20 pA/√Hz at 1 kHz400 pA RMS (2 nA p-p)
100 µA2.5 pA/√Hz at 1 kHz50 pA RMS (250 pA p-p)
10 µA450 fA/√Hz at 1 kHz1.5 pA RMS (7.5 pA p-p)
1 µA150 fA/√Hz at 1 kHz600 fA RMS (3 pA p-p)
100 nA50 fA/√Hz at 100 Hz200 fA RMS (1 pA p-p)
10 nA20 fA/√Hz at 10 Hz150 fA RMS (750 fA p-p)

DC output impedance

RangeMagnitude output impedance
100 mA>500 kΩ
10 mA>1 MΩ
1 mA>10 MΩ
100 µA>100 MΩ
10 µA>1 GΩ
1 µA>1 GΩ
100 nA>1 GΩ
10 nA>1 GΩ

1 Total system, 1 year and ±5 °C from Lake Shore calibration, 24 h and ±1 °C from self-calibration, 95% confidence
2 DC to full accuracy frequency

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