Commissioning an electron microscope: the acceptance tests to witness
By Vvon Engineering Team | Published | Updated
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.
Commissioning should demonstrate the performance and deliverables agreed in the purchase contract. Nominate witnesses, record test conditions and distinguish installation completion from performance acceptance. Warranty commencement, outstanding-work closure and payment milestones follow the signed contract; they do not change automatically when an engineer requests a signature.
Before the engineer arrives
Confirm site readiness before travel is booked, because missing utilities or an unfinished room can prevent useful commissioning.
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.
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.
An approved power-continuity test. If the building transfers to a generator during load shedding, agree a manufacturer-approved transfer or shutdown test with facilities staff. Do not interrupt an energised instrument without an approved procedure. 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, duration and exclusions as agreed in the contract. If acceptance-based cover is required, negotiate it before ordering rather than assume it at handover.
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.
Record passed tests, exceptions, responsible parties and agreed completion dates in the acceptance report. Use the institution's contractual acceptance procedure when a deliverable remains incomplete.
For an electron-microscopy project, Vvon can discuss the instrument, site requirements and proposed commissioning deliverables. Confirm which surveys, manufacturer attendance, acceptance tests and training are included in the quotation. Send your specimen types and draft acceptance criteria to info@vvon.com.bd or call +8801805987890.