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8508A vs 3458/HFL
Functional & Versatility
Parameters
Comments
High Resistance
Measurement (compliance
voltage)
Test Voltage or Full Scale
stimulus = 200V
Test Voltage or Full Scale
stimulus @ 1.2GΩ = 5V
Reduces errors when performing high
resistance measurement (feature available
8508A - 20MΩ to 20GΩ range only)
Tru-Ohms or Offset
Compensated Resistance
technique.
Current Reversal Switched Current
Current reversal reduces errors caused by
thermal emfs as does switched current but
reversal technique has the added benefit of
reducing errors due to self heating
Store RTD temperature
coefficients
Supports a wide variety of PRT &
SPRT sensors
Not Available
PRT calibration coefficients are stored (max
100 probes) within the 8508As internal
memory.
ACAL Not Required
Required every 24hrs or
±1º C
of last ACAL
8508A - Precision without the need for
internal drift corrections. ACAL will overwrite
last stored value and cannot be retrieved.
This might be important for users that
require ‘as found data’.
Auto-zero (A-zero) Range zero is enabled by operator
A-zero should be enabled to
maintain specification
Auto-zero must be enabled on 3458A/HFL if
environment exceeds
±1°C of last Input
zero. Zero/nulling meters before
measurement is accepted metrology
practice.
Low impedance low Current
measurement technology
Yes No
8508A is less intrusive when compared with
conventional meters when measuring low
magnitude current sources. The 8508A
input impedance on the 200uA range is 60
Ohm. This low impedance mimics
technology normally found in Electrometers
and picoampmeters. This compares with 5k
– 10k Ohm on other DMMs.
ACV measurement
technique
Analog True rms
Analog, Synchronous and
Random sampled ac
Digitize sub sampled techniques are useful
when measuring low frequency <1Hz input
signals.