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Quad Digital Voltmeter
SIM970 — 5½-digit voltmeter (4 ch.)
  • True 5½-digit performance
  • Four isolated channels
  • Bright 7-segment LED displays
  • Three decade autoranging to ±19.9999 V
  • 10 MΩ input impedance
  • External trigger for data synchronization
  • Unique continuous autocalibration
  • 90 dB power line frequency rejection

click to enlarge
SIM970 Rear Panel


The SIM970 Quad Digital Voltmeter is designed to make precision DC voltage measurements with excellent long-term accuracy.

For applications in which many voltages must be monitored, up to 16 DVM channels can be put into one SIM900 mainframe. Four voltage ranges from ±199.999 mV to ±19.9999 V can be autoranged or manually selected. An external trigger input allows synchronization of voltage readings on all four channels for critical applications requiring coincidental readings. A BUSY output gives a TTL (logic high) when readings are being taken.

Autocalibration is performed with every reading by sequentially measuring not only the input voltage, but also the ground and the full-scale voltages against a calibrated internal reference. This autocalibration routine virtually eliminates offsets and scale errors, and ensures smooth range-to-range transitions.

SIM900 Mainframe

The bright front-panel LED display shows updated readings three times per second.  Computer access through the SIM900 mainframe (RS-232 or GPIB) permits data logging with 24 bits of resolution. All channels are isolated from ground, and from each other. The SIM970 uses isolated BNC connectors for inputs so coaxial cables can be used for reduced noise pickup.


Specifications  

Number of channels

4

Number of digits

5½ (±199999 counts) [ 1 ]

Full-scale DC voltage ranges

 

Range
1
2
3
4

Voltage
±19.9999 V
±1.99999 V
±999.99 mV
±199.999 mV

Resolution
100 µV
10 µV
10 µV
1 µV

Noise, counts rms [ 1, 2 ]
1.5
0.8
0.8
1.0

Measurement accuracy, ±(% of reading + counts) [ 3 ]

 

Range
   1[ 4 ]
2
3
4

24 Hrs., (23 ± 1) °C
 0.0010 + 2
0.0002 + 2
0.0002 + 2
0.0002 + 4

90 day, (23 ± 5) °C
0.0050 + 2
0.0050 + 2
0.0050 + 2
0.0050 + 6

1 year, (23 ± 5) °C
0.0080 + 2
0.0080 + 2
0.0080 + 2
0.0080 + 6

Transfer accuracy

(24 hour counts error)/2 [ 3 ][ 5 ] (typ.)

Input resistance

10 MΩ ± 1 %,  >3 GΩ selectable on ranges 2 to 4 [ 6 ]

Input terminals

BNC (Amphenol 31-10 or similar)

Input protection

±60 V center to shield,  ±200 V shield to earth

Triggering

Internal, external (TTL), or remote

BUSY output

TTL logic high when busy

Update rate at line frequency [ 7 ]

3.6/s (60 Hz),  3.0/s (50 Hz)

Normal mode rejection at
      line frequency

90 dB (59 Hz to 61 Hz or 49 Hz to 51 Hz)

CMRR (at DC)

125 dB (for 1 kΩ unbalance in the shield)

Settling time

1 s to within 3 counts of final reading on ranges 1 to 3, 8 s on range 4

Display

Red LED, 0.40", with polarity indication. Green LED for range and autorange indication

Operating temperature

0 °C to 40 °C, non-condensing

Interface

Serial via SIM interface

Connectors

BNC (4 front, 2 rear)
DB15 (male) SIM interface

Power

Power supplied by the SIM900 Mainframe, or optionally by a user-supplied DC power supply (+5 V)

Dimensions

3.0" × 3.6" × 7.0" (WHL)

Weight

2.3 lbs.

Warranty

One year parts and labor on defects in materials and workmanship

   

NOTES
[ 1 ] One count is a unit change in the least-significant digit. Greater resolution is available through the remote interface
[ 2 ] Measured over 360 consecutive readings
[ 3 ] Inside SIM900 mainframe following a two hour warmup, autozero ON
[ 4 ] Scale calibration ON
[ 5 ] Within 10 minutes and ±0.5 °C, within ±10 % of the initial value, fixed range, input between 10 % and 100 % of full scale
[ 6 ] Input bias current is <1 pA at 23 °C
[ 7 ] Internal triggering, autozero ON. Rate is double for autozero OFF




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