Lake Shore Model 370 AC Resistance Bridge User’s Manual
1.2 SPECIFICATIONS
Measurement Type:
AC, 4-lead differential, resistance
Number of Inputs
: 1; 16 with Model 3716 Scanner
Measurement Units:
Ohms, Kelvin (with temperature response curve)
Resistance Ranges:
2 m
Ω
to 2 M
Ω
(excitation dependent)
Reading Rate:
10 readings per second (same range and channel)
Range Change Settling:
3 s + filter settling
Channel Change (Scan) Settling:
3 s + filter settling
A/D Resolution:
24 bit
Measurement Resolution:
Range dependent (See Table 1-1)
Accuracy:
Range dependent (See Table 1-1)
Measurement Temp. Co:
(±0.0015% of reading ±0.0002% of
range)/°C
Lead Connections:
V+, V–, I+, I–, V shield, I shield, individual guards
Scanner Lead Connections:
V+, V–, I+, I– for each sensor,
shield common to all
Max Lead Resistance:
100
Ω
+ 10% of resistance range per lead for
current
≤
3.16 mA, 10
Ω
+ 10% of resistance range per lead for
current
≥
10 mA
Input Isolation:
Measurement optically isolated from chassis ground
Common Mode Reduction:
Matched impedance voltage input and
current output, active CMR
Excitation Type:
Sinusoidal AC current source
Excitation Frequency:
13.7 Hz (9.8 Hz and 16.2 Hz alternates)
Excitation Currents:
21 ranges from 3.16 pA to 31.6 mA RMS
Minimum Excitation Power:
10
–18
W into 100 k
Ω
(see Table 1-1 for other ranges)
Maximum DC Current:
4 pA + 1% of excitation current
(1.6 × 10
–18
W into 100 k
Ω
)
Current Protection:
Current leads relay shorted on power-up and range
change
Voltage Ranges:
12 ranges from 2 µV to 632 mV RMS
Voltage Over Range:
20% nominal
Input Impedance:
Approaches 5 × 10
12
Ω
Range Selection Modes:
Manual, Voltage Excitation, Current
Excitation, and Autorange
Scanner Modes:
Manual or Autoscan
Filter:
Settling Times 1 to 200 seconds
Additional Software Features:
Max/Min capture, Linear equation,
user-programmable pause on range and input change
Temperature Conversion
Supported Sensors:
Any resistive sensor including NTC resistors
(e.g., Germanium, Carbon-Glass, Cernox™, Ruthenium Oxide
[Rox™]) and PTC resistors (e.g., Rhodium-Iron RTD)
Requirements:
Requires calibrated sensor and a temperature response
curve loaded into the instrument at the factory or by the user
Temperature Coefficient:
Negative or Positive
Temperature Units:
Kelvin
Low Temperature:
Below 20 mK in a well-designed system
Temperature Resolution:
Sensor and temperature dependent
(Refer to Paragraph 1.2)
Curve Memory:
Space for twenty 200-point curves
Curve Entry:
Entered via front panel, computer interface,
or CalCurve™ option
Curve Format:
Ohm/K, Log Ohm/K
Temperature Control
Control Type:
High resolution digital PID
Control Modes:
Closed Loop PID, Open Loop
Tuning Modes:
Manual PID, Zones
Setpoint Units:
Ohms or Kelvin (with temperature calibration curve)
Setpoint Resolution:
Same as reading display resolution
Control Stability:
Below 10 mK p-p at 50 mK, system dependent
Heater Output Type:
Variable DC current source
Heater Output Isolation:
Optically isolated from chassis and
measurement ground
Output D/A Resolution:
18 bit
Heater Output Ranges:
100 mA, 31.6 mA, 10 mA, 3.16 mA, 1 mA,
316 µA, 100 µA , 31.6 µA
Heater Output Compliance:
10 V
Max Power of Output Ranges:
1 W, 100 mW, 10 mW, 1 mW,
100 µW, 10 µW, 1 µW, 0.1 µW (nominal 100
Ω
)
Heater Type:
Resistive
Heater Resistance Range:
1 – 100 k
Ω
, 100
Ω
for maximum power
Heater Output Gain Accuracy:
±1% of setting
Heater Output Offset (at 0%):
±0.02% of range
Max Heater Noise Current:
<0.005% of range
PID Control Parameters:
Proportional: 0.001 – 1000
Integral: 0 – 10,000 seconds
Derivative: 0 – 10,000 seconds
Manual Output: 0 – 100% (resolution 0.001%)
PID Zone Settings:
10 zones that include setpoint, heater range, PID,
relays, and analog outputs (still)
Still Output:
Up to 1 W of power available using analog output #2
Heater Protection:
Short circuit-protected, disabled with a relay on
power-up, defaults to off range on power-up, selectable heater range
limit, open circuit detection
Scanner Support:
Control with scanned input is supported with reduced
stability
Front Panel
Display Type:
Graphic (8 line by 40 character) vacuum fluorescent
display
Number of Reading Displays:
1 to 8
Reading Display Units:
m
Ω
,
Ω
, k
Ω
, M
Ω
, mK, K
Display Resolution:
4, 5, or 6 digit, user selected
Display Update Rate:
2 readings per second
Reading Display Options:
Ohms, Kelvin, Max, Min, Linear
Other Displays:
Channel number, units, resistance range, excitation
voltage or current, excitation power, control setpoint, heater range,
and heater output
Display Annunciators:
Reading errors, CMR, Alarm, Ramp, Zone,
Remote
LED Annunciators:
Autorange, Excitation Mode, Autoscan
Keypad:
36 key, numeric and specific functions
Interface
IEEE-488.2 Interface Capability:
SH1, AH1, T5, L4, SR1, RL1, PP0,
DC1, DT0, C0, E1
Software Support:
LabView driver for IEEE-488 interface
(consult factory for availability)
Introduction
1-9
