ANALOG DEVICES MAXREFDES183 Portable Precision Calibrator User Guide
- June 9, 2024
- Analog Devices
Table of Contents
ANALOG DEVICES MAXREFDES183 Portable Precision Calibrator
Introduction
The MAXREFDES183# provides the following functions:
- Precision Analog Voltage Output, ±10V (+25% over range)
- Precision Analog Current Output, ±20mA (+25% over range)
- Precision Analog Voltage Input, ±10V (+25% over range)
- Precision Analog Current Input, ±20mA (+25% over range)
- Precision Temperature Measurement (external PT100/PT1000/Thermocouple Type K)
- Precision Temperature Simulator (simulates a temperature sensor)
This Quick Start Guide provides information about:
- First power-up/insert batteries
- Quick explanation on how to measure/source in each mode
- Special menu items
- System calibration
Required Equipment
Supplied by Maxim Integrated®:
- MAXREFDES183#
User Supplied
- Batteries
- USB Charger
- Micro USB Cable
- Digital Multimeter (at least 6.5-digit DMM is recommended)
First Power-Up/Insert Batteries
- The MAXREFDES183# is shipped without Li-ion batteries; the user must purchase and install these.
- The MAXREFDES183# can operate without batteries, by powering the system from a USB charger via a micro-USB cable. To avoid ground loops, please make sure your USB charger is isolated from GND and does not connect to anything else.
- The fully assembled (but without batteries) MAXREFDES183# reference design looks like
- Insert two of the 18650 Li-ion cells (i.e., INR18650-35E).
- Please note: It is necessary to purchase ones with the button-top: Pay attention to the + and – signs on the PCB for each battery and double-check before inserting the batteries
- Push the power-on button (1 to 2 seconds to wake the device up). The display should then show a screen like
Status Bar : System information is displayed here.
Battery Runtime: Estimated remaining battery runtime (hh:mm) at current power usage vs. battery charge level. Note, this time is estimated by the ModelGauge™ M5 algorithm. Initially, it may be inaccurate during the first 1 to 2 charge cycles. The algorithm resets if the batteries are removed.
Battery Charge Level: Display in % of maximum charge.
Battery Charging Indicator: This is displayed if a USB charger is connected, and the battery is charging.
Battery Status: Color indicates battery status.
- As shown in Figure 1, the button to the right of the power button is a Reset button. This button resets the system. Sometimes it is more convenient to go back to the main screen by clicking the Reset button.
- The four banana plugs form a 4-wire port , which allows the system to source or measure voltage or current between the outer pins (GND) and (UIO). The two inner plugs, SNS+ and SNS-, are inputs that allow true 4-wire measurements.
How to Measure/Source in Each Mode
- To source voltage, click on the Voltage Output button
- The next screen will ask the user to enter a voltage. Please enter a voltage between – 12.5V and +12.5V. Note for best accuracy, stay within the range of -10.5V and +10.5V. Once done, click OK. The voltage will be applied between the GND and UIO banana plugs.
- The next screen will show the setting that was typed in before Below that, in smaller font, the current drawn at the UIO port as well as the measured voltage is shown. For example, if you short the output, the setting will still say 9.851V, while the readback should show approximately 0V.
- To source current, click on the Current Output button (Figure 9).
- A new screen will show up and ask to enter a value for the current Please enter a value between -25mA and +25mA. Note for best accuracy, stay within the range of -21mA and +21mA. Once done, click OK.
- The next screen will show the setting that was entered previously. Below that, in smaller font, the current drawn at the UIO port, as well as the measured loop-voltage, is
- To measure voltage, click on the Voltage Input button .
- Connect a voltage source between the UIO and the GND ports. The next screen will directly show the voltage applied between the UIO and the GND plugs. Please note, the voltage range that can be measured is ±12.5V, but the best accuracy is achieved in the range of ±10.5V
- To measure current, click on the Current Input button .
- Connect a current source between the UIO and the GND ports. The next screen will directly show the current flowing between the UIO and the GND ports
To measure temperature (PT100/PT1000/TC Type K), click on the Temperature Measurement button
- The next screen will show how to connect the temperature-sensor (4-wire mode). Connect a sensor as instructed and click OK.
- The next screen will display the temperature based on the selected temperature-sensor type and measured resistance (PTxxx)/voltage (TC).
- The next screen will show how to connect the temperature-sensor (4-wire mode). Connect a sensor as instructed and click OK.
Special Menu Items
- In addition to the normal user functions found in commercial precision calibrators, MAXREFDES183# has some special functions which can be accessed by clicking on the Maxim Logo in the main menu
- After clicking the Maxim logo, an extra menu will be displayed
- Clicking Main Menu leads back to the Main Menu System Settings allows the user to adjust a few settings
- The Sense Measurement inputs use the on-chip programmable gain amplifier (PGA), which allows the calibrator to measure very small voltages between the SNS+ and SNS- inputs
- Battery Info: This screen displays the detailed status of the battery utilizing Maxim’s fuel gauge IC, the MAX17320. Charge Level, Wear Level, and the estimated battery operation time (Time remain) are all displayed
- The Calibrate menu allows the user to calibrate the complete system; details will be explained in the Calibrating the MAXREFDES183# section of the Quick Start Guide.
Calibrating the MAXREFDES183
- For an accurate calibration process, a high-accuracy precision volt and current Meter (or DMM) is required with a recommended minimum of 6.5 digits resolution.
- However, no precision voltage or current sources are needed.
- Ideally, the system should be completely isolated, meaning run from the battery. Even if the USB charger is isolated, there is still possible capacitive coupling of noise between the mains supply lines and the MAXREFDES183# system. The same concern is true for mains-powered precision meters; even very small 50/60Hz noise that is coupled in might affect the performance/accuracy of the resulting calibration factors.
- As long as only one side is connected to the mains (i.e., the precision meter), there is no potential for ground loop-inducing noise, and so there should not be any issues.
- Before the MAXREFDES183# is calibrated, let your precision meter as well as the MAXREFDES183# warm up and reach stable thermal levels, for example, let both operate for 15 to 30 minutes. Note, this is usually also recommended practice for precision equipment like 6.5- or 8.5-digit DMMs.
- Calibrate Voltage: Click the Calibrate Voltage button
- A screen will show how to connect the precision DMM.
- The MAXREFDES183# will now produce a “high” voltage of approximately 10V between the UIO and GND
- Next, the MAXREFDES183# will produce a “low” voltage of approximately “-10” between the UIO and GND (Figure 26). It should be stable in at least 5 digits, if not, then something is wrong with your setup.
- The MAXREFDES183# will calculate and show the results for the gain and offset errors. The results for the DAC in the MAX22000 should look like. If the results make sense, the display will show “DAC results are plausible
- Next, the MAXREFDES183# will show the results from calibrating for the ADC in the MAX22000. The procedure is identical to that for the DAC to generate gain and offset error data
- The MAXREFDES183# has onboard nonvolatile memory (FLASH) which is used to store calibration data for the DAC and ADC in MAX22000
- The next step in the calibration process is to enter a description or name for the new calibration data. After clicking OK, a keyboard will show up and allow the user to enter free-form text, that will be saved in the FLASH together with the calibration data.
- Calibrate Sense Inputs: Calibrating the SNS+/SNS- inputs follows the same procedure as calibrating voltage, with the exception that, for this operation, the UIO pin must be connected to the SNS+ pin and GND must be connected to the SNS- pin.
Revision History
REVISION NUMBER| REVISION DATE| DESCRIPTION| PAGES
CHANGED
---|---|---|---
0| 8/21| Initial release| —
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Maxim Integrated is a registered trademark and ModelGauge and Cycle+ are
trademarks of Maxim Integrated Products, Inc.
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