Instrument Circuitry – Reference 3000 Schematic/Block Diagrams
24
Figure 3-6
DC-DC Power Conversion
Notes for Figure 3-6:
Note the ground isolation between the input power and the Reference 3000 circuitry. The Reference
3000 chassis is connected to the Floating Instrument Ground. Transformers and isolators are the only
components connected between the grounds.
The 300 kHz power-supply sync signal is derived from the same clock used to control data acquisition.
Data points taken at an integer multiple of 3.333
s/point are synchronized with the power supply,
minimizing the effect of power-supply noise on the data.
Additional circuitry that is not shown protects the Reference 3000 against ESD (electrostatic discharge)
and electrical surges. Note that the Reference 3000 is also protected against damage if an incorrect
polarity power input is connected to the unit.
The incoming DC voltage must be between 22 and 26 V. With inputs below 22 V, the PWM (Pulse
Width Modulator) may be unable to regulate the supply. Above 26 V, the PWM may not start up.
Caution:
Do not use a DC power source other than the AC-adapter model provided with
your Reference 3000. Other replacements may void the performance and/or safety characteristics of the
Reference 3000.
Power input voltages less than 20 V or greater than 26 V can damage the Reference 3000’s power supply.
