LOAD-CELL PEAK-HOLD UPPER BOARD
LP1 (Ultra-Low Tempco) LP2 (Low Tempco)

FEATURES
Peak detector with meter HOLD
Differential preamplifier with gains from 20 to 800
Floating 5, 10, 15 V dc excitation supply
Up to 115 mA at 10 V dc to drive four 350 ohm bridges in parallel
Ratiometric operation with remote excitation sense
4 or 6-wire bridge connection
Front-panel accessible fine span and finebridge balance adjustments
Peak-reset or push-to-cal pushbutton
Deadload offset to ±60% of input
Low tempco: ±10 ppm/°C (LA1), ±30 ppm/°C (LA2)

APPLICABLE INSTRUMENTS
204B (3 3/4 digits)
2003B (4 1/2 digits)
2004 (4 3/4 digits)

The LP1 and LP2 are upper-board options which convert Models 204B, 2003B and 2004 DC voltmeters into strain gauge/microvoltmeters with peak detection and display hold capability. A front-panel pushbutton can be used for peak-reset or push-to-cal.

Option LP1 uses wirewound resistors, which provide an ultra-low tempco of ±0.001%/°C (±10 ppm/°C). It is recom-mended for use with Model 2004, a high-accuracy 4 3/4 digit voltmeter.

Option LP2 uses metal-film resistors, which provide a tempco of ±0.003%/°C (±30 ppm/°C). It is recommended for use with Models 204B and 2003B.The LP1 and LP2 are useful for dynamic test applications which use pressure transducers, and/or load cells that require bridge excitation and preamplification of microvolt signals.

PREAMPLIFIER AND EXCITATION SUPPLY
The LP1 and LP2 are used in conjuction with the "-3" and "HZ" DC input configurations of the host meter. It adds a differential preamplifier, which can be configured for gains from 20 to 800, and a floating constant-voltage excitation supply, which can be configured for 5, 10 or 15 V dc. The supply can provide 115 mA at 10 V dc, so that one LP board can excite up to four 350l bridges in parallel. The reference used in the A/D converter of the host meters is derived from excitation voltage sense lines for true ratiometric operation.

PEAK-DETECT AND HOLD CIRCUIT
The LP1 and LP2 allow the host DPM to track the output of the preamplifier as long as the signal is increasing. When the signal decreases, two digital outputs go low. One of these is connected to the DPM's HOLD input. The other is available for connection to external equipment (e.g., printer) or for indication of a peak reading. The period of time that the DPM will remain in hold without reset is based upon the rate of signal decrease and will range from a few seconds for a slow decrease to several minutes for a large step function.

SPECIFICATIONS

PREAMPLIFIER
Input configuration: Differential, ratiometric
Gain range: 20 to 800
Preamplifier output swing: ­0.5 V to +4.0 V
Coarse-span adjustment: 125 overlapping ranges with fine adjustment
Fine-span adjustment: Front-panel potentiometer
Coarse-bridge balance adjustment: ±60% of bridge output with external resistor
Fine-bridge balance adjustment: Front-panel potentiometer

Operation of LP upper board with DPM main board. The excitation supply is referenced to ground through the external bridge and the ratiometric reference circuit, thereby providing high immunity to power-line and load variations. The peak reading is held digitally by meter HOLD, thereby eliminating any droop in reading.

NOISE REJECTION
NMR, 50/60 Hz: 25 dB (to be added to NMR of host DPM)
CMR, SIG LO to SIG GND: 80 dB, DC to 60 Hz
CMV, SIG LO to SIG GND: ±1 V, DC to 60 Hz
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

ACCURACY AT 25 °C
Zero tempco referred to input (RTI), typ: ±0.3 µV/°C
Zero tempco referred to output (RTO), typ: ±0.6 µV/°C
Span tempco, LA1: ±0.001%/°C(±10 ppm/°C)
Span tempco, LA2: ±0.003%/°C (±30 ppm/°C)

EXCITATION SUPPLY
Configuration: Constant-voltage
Voltage sense: Internal or remote
Bridge connection: 4 or 6-wire
Voltage settings: 5, 10, 15 V dc, (jumper-selectable)
Load current, max: 125 mA at 5 V, 115 mA at 10 V, 67 mA at 15 V

DIGITAL OUTPUTS
Type: Open-collector output
Sink capability: 6 mA at 5 V dc
State after peak condition: LO

POWER
AC input voltage: 120/240 V ac +10%/­15%
AC frequency: 50/60 Hz
Power consumption at max excitation load: 0.5 W

ENVIRONMENTAL
Operating temperature: 0 to 50°C
Storage temperature: -40 to +85°C
Relative humidity: 95% at 40°C(non-condensing)

MECHANICAL
Form factor: Newport DIN 1A upper board
Dimensions: 3.35 x 4.69 in (85 x 119 mm)
Connector: 36-pin, double-row, solder-type