Commissioning an electron microscope: the acceptance tests to witness
What to insist on seeing before signing the installation report, from the low voltage resolution figure through to the drift and contamination checks, and why your negotiating position disappears the moment the form is signed.
The installation engineer finishes, prints a report and asks for a signature. The person holding the pen is often a departmental head who was not in the room for the tests, and the tests were the point of the visit. Once that form is signed the warranty clock starts, and every remaining question becomes a service request rather than an obligation. Acceptance is the last moment when the supplier has to prove the instrument meets the contract.
Before the engineer arrives
Most failed commissioning visits fail on site readiness, not on the instrument.
The site survey results, in writing, accepted by the manufacturer. Floor vibration, stray alternating magnetic field, acoustic noise and room temperature stability, all measured in the actual room with the building running normally. A survey done at nine at night in an empty building is not a survey.
Services complete and tested: power with the specified earthing arrangement, cooling water at the stated flow and temperature, compressed air or dry nitrogen, and the exhaust route for the pumps.
The room finished and clean before the crate opens. No painting, drilling or ceiling work after the column is in place.
The contract specification sheet printed and in the room. That page is the reference for every test that follows.
Someone named to witness, with the authority to refuse a test and time booked to attend the whole visit.
The resolution test, and how it can be gamed
Resolution is quoted at a stated accelerating voltage and a stated working distance. Both conditions matter, and a resolution image taken at a different working distance or a different voltage from the one in the contract does not demonstrate the specification.
Insist on the low voltage figure. High voltage resolution is where instruments look similar. Low voltage performance is where they differ, and it is what most real samples need. If a low kV resolution figure was in the quotation, witness it.
Use the standard specimen the manufacturer specifies, normally gold particles on carbon, and record which one was used.
Take the raw image file, not a printout, and keep it with the acceptance documents so a future dispute has evidence.
Check magnification against a certified standard, and ask for the certificate for the standard itself. An uncertified grating proves nothing about traceability.
If an EDS detector is fitted, witness the energy resolution measurement at a stated count rate, take a spectrum from a clean known material, and confirm there are no unexpected peaks from the chamber or the holder.
The tests people skip
Resolution gets witnessed because it is in the brochure. The tests that predict day to day usability are usually left out.
Image drift. Capture a high magnification field, wait several minutes without touching anything, capture it again and compare. Persistent drift after the stage has settled points to a thermal or mechanical problem in the room, and it is much easier to argue about before acceptance.
Stage repeatability. Move away and return to a marked feature several times. Backlash makes automated mapping and long acquisitions unreliable.
Contamination rate. Park the beam on a clean standard for a defined time, then image the area at lower magnification. A dark square appearing immediately means a dirty column, chamber or specimen exchange route, and it is far better found now.
Interference from the building. Run at high magnification with the room in its normal working state: air conditioning on, lights on, doors as they will be, and somebody using the corridor. A regular ripple in the image at mains frequency means a stray alternating field, and on a 50 Hz supply it has a characteristic look that an experienced engineer will recognise immediately.
A generator changeover. If the building transfers to a generator during load shedding, ask for the instrument to be observed through a transfer. It is the most Bangladesh-specific test here and the one most likely to surface after the engineer has flown home.
What the handover document must contain
Every acceptance image and measurement, with the conditions recorded, attached to the report rather than described in it.
The site survey results as measured, so that a future problem can be compared against the starting condition.
Consumables listed with part numbers: filaments or emitters, apertures, detector windows, stubs and vacuum consumables. This is the list a purchasing office needs and never receives.
Software licences, dongles and support portal accounts registered to the institution rather than to an individual who will leave.
Warranty start date tied to acceptance, not to shipment or to arrival at customs. A warranty that started when the crate left the factory has already been partly spent on the sea voyage.
The first service date, what it includes, who performs it and their response time to Dhaka.
Training dates with named attendees, at least two of them. An instrument with one trained user has a single point of failure.
Sign when the tests are done and the documents are complete, and not before. A supplier who has not yet been paid the final instalment answers the telephone.