Welch Allyn Spot Vital Signs 4400, Service Manual

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Test Limits
Ground continuity (see Note above) Ground continuity from EP stud (equipotential terminal)* to the Gnd pin
of the IEC power connector shall be no greater than 0.1 ohms.
Leakage current (see Note above) Leakage current shall be less than 500 µA from EP stud* to mains (Line
and Neutral pins of the IEC power connector).
Insulation resistance Dielectric strength shall be 500 V (DC) EP stud* to IEC mains (Line and
Neutral pins of the IEC power connector), and insulation resistance is
measured.
* To locate the equipotential terminal, see “Controls, indicators, and connectors."
Devices with an External Power Supply
The power bricks are CB Certified and UL Listed; they meet ALL of the requirements that the
Medical Device standard requires for power supplies. The manufacturer is required to perform
100% electrical safety testing on all of their power bricks prior to shipment. Welch Allyn does not
perform nor recommend testing on these external power bricks because additional testing would
put undue stress on the insulation system and possibly cause premature failures in the field. Open
case repairs of devices with external power supplies are only dealing with DC circuitry and robust
isolation circuits built into the printed circuit boards. No additional after-servicing testing is
required in that instance. The patient isolation systems within the device (Temperature Probe,
SpO2 sensor, etc.) all have visible isolation gaps built into the printed circuit board. The quality
control on the PCB and the thorough type-testing performed by the testing agency (ETL)
eliminates the need for further testing on the devices that are downstream from the mains
isolation device.
Devices with an Internal Power Supply
The internal power supplies are CB Certified and UL Registered. These power supplies are an open
frame style (no protective enclosure). Therefore, the products that contain an internal power supply
require electrical safety testing. Open case repairs of devices with an internal power supply require
the recommended testing because those devices contain the open frame power supply, and the
testing involves the manipulation of wiring that carries 120 or 240 volts AC. Welch Allyn does not
recommend HiPot / Dielectric Withstand testing because of a potential stress on the insulation
system, which could cause premature failures.
Basic functional verification
Basic functional verification checks
NOTE
Calibration is available only with the service tool, Gold edition.
These tests verify basic functionality of the NIBP, SpO2, and thermometry parameters. These tests
support the requirements of routine preventive maintenance. However, they are not a substitute
for the complete functional tests available with the service tool, Gold edition. Welch Allyn
recommends using the service tool, Gold edition, to perform preventive maintenance and
verification of the device when completing a repair.
70 Functional verification and calibration overview