ADLINK MCM-100/102 Deployment Calibration Guide

Floating ground signal source (such as IEPE sensor or ungrounded equipment): Pseudo differential mode should be selected, where the negative terminal is connected to ground through a 20 k Ω resistor to provide a reference potential and avoid common mode voltage exceeding the limit.

3.2 Coupling Method and IEPE Incentive

DC coupling: retaining the DC component in the signal, suitable for low-frequency vibration or static strain measurement.

AC coupling: Remove DC bias through a 0.4 Hz high pass filter (-3 dB), suitable for accelerometer signals to avoid amplifier saturation.

IEPE current source: When IEPE (2 mA constant current) is enabled, the system automatically switches to AC coupling and provides 24V compliance voltage, which can directly drive standard IEPE accelerometers. Attention: If the sensor does not require excitation, the IEPE current must be turned off by software, otherwise it will cause measurement errors.

3.3 Anti aliasing filtering and frequency response

The Δ - ∑ ADC is equipped with multi-stage FIR digital filters, providing linear phase and 100 dB stopband attenuation. But the front-end is still equipped with a simple RC low-pass to suppress out of band high-frequency noise. The document provides two modes:

High resolution mode (sampling rate ≤ 52.734 kHz): -3 dB bandwidth of approximately 0.49 × fs, passband flatness ± 0.01 dB (20 Hz~20 kHz).

High speed mode (sampling rate 52.734~128 kHz): The bandwidth is correspondingly expanded, but the noise is slightly increased (65 μ Vrms vs 50 μ Vrms).

Engineers should select an appropriate sampling rate based on the target fault frequency (such as bearing characteristic frequency), follow the Nyquist criterion, and use anti aliasing filters to avoid false frequency component folding.

Trigger mechanism and collection mode selection

MCM-100/102 supports flexible trigger sources (software, external simulation, external digital) and multiple trigger modes to adapt to different working conditions.

4.1 Source of Contact

Software trigger: immediate execution, suitable for simple startup collection.

External simulation trigger: Select any AI channel as the source, and set "below low threshold" or "above high threshold" to generate the trigger. The resolution is 24 bits and the level range is ± 10V.

External digital trigger: Receive rising or falling edge through GPI/O pin, minimum pulse width of 20 ns, TTL level (3.3V). Suitable for external tachometers or proximity switches.

4.2 Trigger Mode Application Scenarios

Applicable scenarios of the mode

Record the complete waveform after the post trigger fault event is triggered for transient analysis.

Pre trigger collects N samples (N ≤ 8k/channel) before triggering, suitable for capturing precursors of sudden impacts.

Middle trigger simultaneously collects specified length data before and after triggering, balancing the information before and after.

Gated triggering is only collected during high (or low) trigger levels and is suitable for signals with varying duty cycles.

Retragger responds to multiple triggers during a single acquisition process and is suitable for continuous shock sequences.

Key constraint: The total number of samples (M+N) for pre trigger and mid trigger must not exceed 8k samples/channel, otherwise the trigger signal will be ignored.

Calibration process and accuracy maintenance

To ensure long-term measurement accuracy, the equipment provides factory calibration constants (stored in EEPROM) and user automatic calibration functions.

5.1 When calibration is needed

Environmental temperature changes exceeding ± 10 ℃

Regular maintenance every year

After replacing the sensor or extending the cable

5.2 Automatic calibration steps

Preheating: After powering on, run for at least 15 minutes to stabilize the internal temperature.

Run software calibration program (called by UD-DASK or MAPS Core API provided by ADLINK).

No external signal source required, onboard reference voltage and digital potentiometer automatically correct offset and gain errors.

Save constants: The calibrated new constants can be stored in the user specific EEPROM area, and the original factory constants are permanently retained and can be restored at any time.

Attention: The typical gain error after calibration is ± 0.15%, and the offset error is ± 0.15 mV, ensuring high-precision DC measurement.

Advanced applications of programmable GPI/O

In addition to AI, the platform provides 2 channels of 3.3V TTL programmable I/O (shared DGND), which can be configured through software to perform one of the following functions (select only one at a time):

6.1 Static Digital I/O

Software polling to read or output levels, suitable for controlling indicator lights, relays, or reading simple states.

6.2 Frequency/Event Counter

Measure the external pulse frequency, up to 4 MHz, and set the effective rising or falling edge. Suitable for speed calculation or flow meter pulse accumulation.

6.3 PWM output

Generate adjustable frequency and duty cycle square waves with a maximum frequency of 4 MHz by setting Pulse_initial-cnt and Pulse_length_cnt. Calculation formula:

text

F_PWM = F_Timebase / (Pulse_initial_cnt + Pulse_length_cnt)