Electrical — Maintenance & Use

Author:Matthias Boularot
Created on:24 Feb 2026

Routine checks, cleaning, and lab use of the Additel ADT220 and B&K Precision 5491A — the two electrical instruments that support mass flow calibrations.

Role in the Calibration System

These instruments measure the device under test's analog output signal during mass flow calibrations: DC voltage (0–5 V, 0–10 V) or DC current (4–20 mA). The ADT220 can also source a setpoint signal (voltage or current) to mass flow controllers that accept an analog command input. This source function is operationally useful but not metrologically sensitive — the reference mass flow is always measured by the molbloc/molbox system, so the setpoint only needs to be close enough to place the calibration point in the right region of the DUT's range.

Electrical measurement uncertainties are orders of magnitude tighter than mass flow measurement uncertainties. These instruments contribute negligibly to the overall calibration uncertainty budget.

Additel ADT220
Handheld multifunction loop calibrator. Measures and sources DC voltage, mV, and current. Provides 24 V loop power. Battery-powered (Li-ion, approximately 15 hours of continuous use). (ADT220 User Manual, sections 5–7; ADT220 Spec Sheet)
B&K Precision 5491A
Bench-top 50,000-count dual display multimeter. Measures DC/AC voltage, DC/AC current, resistance, frequency, and continuity. Mains-powered (100/120/220/240 V AC selectable). (5491A Manual, Section 1; 5491A Data Sheet)

Routine Checks

Before each use, verify the instrument is functioning correctly.

ADT220

  • Press the power key and verify the main interface loads without error messages. (ADT220 Manual, section 9.1.1)
  • Check the battery indicator in the status bar. If the battery icon flashes, charge the calibrator before use — the unit powers off automatically when the battery is extremely low. (ADT220 Manual, section 5.3)
  • Inspect the TC150S-4PA test leads for damaged insulation or exposed metal at the connectors. Do not touch the metal parts of the test lead interface to avoid introducing thermo-emf errors. (ADT220 Manual, section 4)

B&K Precision 5491A

  • Press the Power button to the IN position. The primary and secondary displays light for approximately 2 seconds while the meter runs its internal self-test, then resume the stored measurement configuration. (5491A Manual, section 2-3)
  • Verify the line voltage selector on the rear panel matches the local supply voltage (230 V for our lab). An incorrect setting can damage the meter or blow the line fuse. (5491A Manual, section B-3)
  • Inspect test leads for damaged insulation or exposed metal. Check test lead continuity. Replace damaged leads. (5491A Manual, section 1-5)

Cleaning

ADT220

  • Clean regularly to prevent water penetration into the calibrator. Wipe exterior surfaces and keep the electrical jacks free of debris. (ADT220 Manual, section 4)

B&K Precision 5491A

  • Switch the power off and disconnect the power cord from the AC outlet. Wipe surfaces with gauze or a soft cloth soaked with diluted neutral detergent. Do not get the cloth too wet — prevent liquid from penetrating into the case. Let the instrument dry completely before reconnecting power. (5491A Manual, Appendix B-2)

Manufacturer References

The manufacturer manuals are the authoritative reference for detailed operating procedures, system calibration, and troubleshooting.