Calibration
MORE COMPACT CALIBRATOR The MAXREFDES183# reference design (see Figure 2) is a software-configurable battery- powered precision calibrator that is compatible with common industrial analogue input and output, and voltage and current ranges. It also provides the following functions:
Precision analogue voltage output, ±10V (+25 per cent over range)
Precision analogue current output, ±20mA (+25 per cent over range)
Precision analogue voltage input, ±10V (+25 per cent over range)
Precision analogue current input, ±20mA (+25 per cent over range)
Precision temperature measurement (external PT100/PT1000/thermocouple type K)
Figure 5. Analogue output voltage stability (drift) of the MAXREFDES183#. Precision temperature simulator
Compared with bulky desktop calibrators, this reference design calibrator measures only 108mm × 83mm × 36mm and weighs just 283g. The functional diagram for the MAXREFDES183# is shown in Figure 3.
FEATURES
The MAXREFDES183# is based on the MAX22000, a software-configurable, industrial-grade analogue I/O that can be used to measure voltage and current with additional inputs for measuring temperature (TC and RTD). This IC has a fast-settling 18-bit DAC and a 24-bit sigma-delta ADC, each of which use a stable 5ppm/°C internal voltage reference, accurate to within 0.01 per cent at 25°C. Linear range is set at 105 per cent, while full-scale range is set at 125 per cent of the nominal range (for example, ±10.5V and ±12.5V respectively for a nominal range of ±10V), while a low noise on-board PGA has high voltage and low voltage input ranges to support RTD and TC measurements by the ADC. The IC is configured using a high speed SPI bus that also transports conversion results. Operating from 2.7V to 3.6V analogue and digital supplies, and up to ±24V high voltage supplies, it is available in a 64-pin LGA package and operates over the –40°C to +125°C industrial temperature range. The reference design also features the MAX32625, an ultra low power Arm Cortex-M4 microcontroller with 512kB flash and 160kB SRAM, which interfaces to the MAX22000
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Figure 6. The MAXREFDES183# calibration menu. June 2025 Instrumentation Monthly
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