Agilent Technologies 34970A, Service Manual, Page: 19 / 273

DC Measurement and Operating Characteristics
DC Measurement Characteristics
[1]
DC Voltage
Measurement Method:
A/D Linearity:
Input Resistance:
100 mV, 1 V, 10 V ranges
100 V, 300 V ranges
Input Bias Current:
Input Protection:
Continuously Integrating,
Multi-slope III A/D Converter
0.0002% of r 0.0001% of range
Selectable 10 M
Ω
or >10 G
Ω
10 M Ω ± 1%
< 30 pA at 25 ° C
300 V on all ranges
Resistance
Measurement Method:
Offset Compensation:
Max. Lead Resistance:
Input Protection:
Selectable 4-wire or 2-wire Ohms,
Current source reference to LO input
Selectable on 100
Ω
, 1 k
Ω
, 10 k
Ω
ranges
10% of range per lead for 100
Ω
and
1 k Ω ranges. 1 k Ω on all other ranges
300 V on all ranges
DC Current
Shunt Resistance:
Input Protection:
5
Ω
for 10 mA, 100 mA; 0.1
Ω
for 1A.
1.5A 250 V fuse on 34901A module
Thermocouple
Conversion:
Reference Junction Type:
Open T/C Check:
ITS-90 software compensation
Internal, Fixed, or External
Selectable per channel. Open > 5 k
Ω
RTD
α
= 0.00385 (DIN) and 0.00391
Thermistor
44004, 44007, 44006 series
Measurement Noise Rejection 60 Hz (50 Hz)
[2]
DC CMRR:
Integration Time
200 PLC / 3.33s (4s)
100 PLC / 1.67s (2s)
20 PLC / 333 ms (400 ms)
10 PLC / 167 ms (200 ms)
2 PLC / 33.3 ms (40 ms)
1 PLC / 16.7 ms (20 ms)
< 1 PLC
140 dB
Normal Mode Rejection
[3]
110 dB
[4]
105 dB
[4]
100 dB
[4]
95 dB
[4]
90 dB
60 dB
0 dB
DC Operating Characteristics
[5]
Function
DCV, DCI, and
Resistance:
Digits
[6]
6
1
⁄
2
6
1
⁄
2
5
1
⁄
2
5
1
⁄
2
4
1
⁄
2
Readings/s
0.6 (0.5)
6 (5)
60 (50)
300
600
Additional
Noise Error
0% of range
0% of range
0.001% of range
0.001% of range
[7]
0.01% of range
[7]
Single Channel Measurement Rates
[8]
Function
DCV, 2-Wire Ohms:
Thermocouple:
RTD, Thermistor:
Resolution
6
1
⁄
2
(10 PLC)
5
1
⁄
2
(1 PLC)
4
1
⁄
2
(0.02 PLC)
0.1 ° C (1 PLC)
0.1 °
C (0.02 PLC)
0.01 ° C (10 PLC)
0.1 ° C (1 PLC)
1
°
C (0.02 PLC)
Readings/s
6 (5)
53 (47)
490
49 (47)
280
6 (5)
47 (47)
280
Autozero OFF Operation
Following instrument warm-up at calibration temperature ± 1 ° C
and < 10 minutes, add 0.0002% range additional error + 5 µ V.
Settling Considerations
Reading settling times are affected by source impedance,
low dielectric absorption characteristics, and input signal changes.
[1] 300 Vdc isolation voltage (ch-ch, ch-earth)
[2] For 1 k Ω unbalance in LO lead
[3] For power line frequency ± 0.1%
[4] For power line frequency
±
1%, use 80 dB.
For power line frequency
±
3%, use 60 dB.
[5] Reading speeds for 60 Hz and (50 Hz) operation; autozero OFF
[6] 6
1
⁄
2
digits=22 bits, 5
1
⁄
2
digits=18 bits, 4
1
⁄
2
digits=15 bits
[7] Add 20 µ V for DCV, 4 µ A for DCI, or 20 m Ω for resistance
[8] For fixed function and range, readings to memory,
scaling and alarms off, autozero OFF
1
Chapter 1 Specifications
DC Measurement and Operating Characteristics
17