Model 202A-S - Low-Cost, 3 1/2 Digit Strain/Microvoltmeter

4 1/2 DIGIT STRAIN / MICROVOLTMETER
MODEL 2002A-S / 2002B-S & 3002-S

1/8 DIN (2A) Case

Connections Diagram

STANDARD FEATURES
Programmable microvolt preamplifier
Isolated 10-24 Vdc bridge excitation supply
Independent bridge-balance, zero & span adjustments
±1,999-count display span
120 dB CMR, 70 dB NMR
Bright, 14.2 mm (0.56 in) LED display
Automatic zero and polarity
Display hold and test
115/230 Vac power
EMI/RFI filter for AC power
Screw-terminal barrier strip
Short (4.1 in, 104 mm deep) 1/8 DIN case

OPTIONS
Isolated 9-32 Vdc power
Isolated 26-56 Vdc power
NEMA-4 splash-proof lens cover

Model 2002A-S is a low-cost 4 1/2 digit (±19,999 count) panel meter for indication-only applications that require bridge excitation and resolution down to 1 µV. Zero, span and bridge-balance potentiometers are accessible behind the lens, so that the 2002A-S can be adjusted to read out directly in engineering units for a wide range of bridge inputs or other low-level signals. A ratiometric reference from the bridge excitation eliminates AC line and load regulation errors and reduces overall meter span tempco to 0.01% of reading/°C. Overall meter accuracy is 99.98% at 25°C.

The 2002A-S is housed in a short 4.1 in (104 mm) 1/8 DIN case to fit where space is limited. Power options include isolated 9-32 Vdc and 26-56 Vdc. A splash-proof lens cover which meets NEMA-4 requirements allows the 2002A to be used in harsh industrial environments.

APPLICATIONS
The 2002A-S is ideal as a digital indicator for pressure cells and metal-foil load cells. It can also be used as a low-level, high-impedance process meter with zero and span adjust- ments or as a DC voltmeter with resolution down to 1 µV, as required by 50 mV current shunts.

BRIDGE EXCITATION SUPPLY
The excitation supply is transformer-isolated to 500 V ac from the rest of the meter and provides up to 30 mA at 10 Vdc of output current. A multiturn potentiometer accessible behind the lens allows adjustment of output voltage from 10 to 24 Vdc.

MICROVOLT PREAMPLIFIER
The preamplifier provides an input resistance in excess of 1 G without bridge balance. Gains of 1, 10 and 100 are selectable by plug-in jumpers and provide meter resolutions of 100, 10 and 1 µV/count, respectively. Typical offset drift is only 0.3 µV/°C.

SPECIFICATIONS

ANALOG INPUT

Range	±20 mV	±200 mV	±2 V
Resolution	1 µV/count	10 µV/count	100 µV/count
Preamplifier gain	100	10	1

Input resistance: 1 Gohm without bridge balance
Bias current: 1 nA typ, 5 nA max
Gain attenuator: Adjustable from 0.001 to 1
Bridge-balance range: ±1.5 mV with 350 bridge
Zero-adjustment range: 19,999 to +19,999 counts
Span-adjustment range: 0 to 19,999 counts

REFERENCE
Configuration: Differential, ratiometric
Internal from excitation supply: 1.0 V with 9.5 kohm source resistance at 10 V excitation
External, optional: 1.0 V 50%/+100% with 680 kohm input resistance

ACCURACY AT 25°C
Maximum Error: ±0.01% of span ±2 counts

Reference	Internal	External
Bridge-balance tempco	±0.5 µV/°C	±1.0 µV/°C
Zero tempco	±0.5 counts/°C	±1.0 counts/°C
Span tempco	±0.005% of span/°C	±0.01% of span/°C

Full-scale step response: 1 s
Warmup to rated accuracy: 10 min

NOISE REJECTION
NMR, SIG HI to SIG LO: 80 dB at 50/60 Hz for 20 mV range, 66 dB at 50/60 Hz for 200 mV and 2 V ranges
CMR, SIG GND to PWR GND: 120 dB, DC to 60 Hz
CMV, SIG GND to PWR GND: 1500 Vp per HV test, 354 Vp per IEC spacing

ANALOG-TO-DIGITAL CONVERSION
Technique: Dual-slope, average-value
Signal integration period: 100 ms
Read rate: 2.5/s

BRIDGE EXCITATION SUPPLY
Output voltage: Adjustable from 10 to 24 Vdc
Output current: 30 mA max at 10 Vdc decreasing to 12 mA max at 24 Vdc
Line regulation*: 0.01% typ, ±0.04% max for 10% change of AC power voltage
Load regulation*: ±0.15% typ, ±0.5% max from zero to max load
Ripple at 50/60 Hz: ±0.01%
Tempco: ±0.02%/°C
*The internal reference is derived from the excitation voltage for ratiometric operation. This eliminates load and line regulation errors and reduces other errors as indicated under accuracy at 25°C.

DISPLAY
Type: 7-segment, red LED
Height: 0.56 in (14.2 mm)
Symbols: 1.8.8.8.8
Decimal points: Four positions programmable by jumpers behind lens or at connector, sink 10 mA to SIG GND
Overrange indication: Four least-significant digits flash

DIGITAL SIGNALS
Input signals: Display hold, blanking, display test, decimal point select
Level, Input signals: TTL or 5 V CMOS compatible

POWER
AC voltages: 115 or 230 Vac ±15%
AC frequency: 49-440 Hz
DC voltages: 9-32 Vdc, isolated to 300 Vp; 26-56 Vdc, isolated to 300 Vp
Power consumption: 4.0 W
Output Voltages: +4.7 Vdc and 4.7 Vdc ±5%, 10 mA max

ENVIRONMENTAL
Operating temperature: 0 to 60°C
Storage temperature: 40 to +85°C
Relative humidity: 95% at 40°C (non-condensing)

MECHANICAL
Dimensions: Newport DIN1A (1/8 DIN) case (see Mechanical section for drawings)
Weight: 15 oz (425 g)
Case material: 94V-0 UL-rated polycarbonate
Connector for signal, power and excitation: Screw-terminal barrier strip (standard)
Connector for display control lines: 36-pin PCB edge connector (optional)

Model 2002B-S w/electrically-floating excitation supply

Model 2002B-S w/electrically-floating excitation supply