AbhilekhUltra-low temperature · −80 °C · dry iceULT freezer monitoring at −80 °C
At −80 °C the electronics are the problem. Batteries lose capacity, displays stop refreshing, and adhesives let go — so the instrument belongs outside the freezer and only the probe goes in.
Ultra-low temperature storage holds the highest-value inventory in most life-science facilities: cell banks, viral vectors, mRNA drug substance, clinical trial retains. It is also the hardest environment to instrument, because almost nothing consumer-grade survives it. Lithium cells deliver a fraction of their rated capacity at −80 °C, LCDs freeze, and a logger placed on a shelf inside the chest will eventually fail in a way that looks like a temperature excursion.
The standard answer is a split design: the measuring instrument sits outside at room temperature where its battery, radio and display behave predictably, and a thin Class-A PT100 probe passes through the port or the lid gasket to the measuring point inside. Dry-ice shipments follow the same logic, with the added constraint that the record has to be readable on arrival by someone who has never seen your software.
ABH-100-D is built for exactly this split, and ABH-300 extends it to four probed positions where a large chest or a mapped ULT bank needs more than one point.
The expectations behind the record
What an inspector or auditor looks for in this use case, and the framework each expectation comes from.
Measurement at the storage temperature, not extrapolated to it
A sensor specified to −40 °C cannot be used to evidence −80 °C storage. The probe's rated range must cover the operating band with a calibration that brackets it.
Continuous record through alarm conditions and power loss
ULT excursions develop over hours, and the value of the record is precisely in the window when the facility was in trouble. Logging must continue on local power and local memory.
Evidence a recipient can verify independently
For dry-ice shipments the arrival record must be self-contained and tamper-evident — the receiving site should be able to confirm the trip without access to the shipper's account.
Excursion assessment against product stability data
The record answers what happened; the disposition decision needs that record joined to the product's stability profile, with the assessment and CAPA attached and signed.
The failure modes nobody budgets for
Every one of these is a real reason monitoring programmes lose their audit trail — or lose the trust of the people who work with them.
Batteries that die in the cold
Cell capacity at −80 °C is a small fraction of the datasheet figure at 20 °C. A logger sitting inside the chest reports low battery, then reports nothing, in the middle of the study you needed it for.
Ports and gaskets you are not allowed to modify
Drilling a qualified ULT freezer is not an option. The probe has to fit an existing access port or pass the lid gasket without compromising the seal.
Frost, condensation and repeated thermal shock
Every lid opening cycles the probe tip between −80 °C and ambient with condensation on the way back. Sheath and cable have to survive that, not just tolerate it once.
Dry ice sublimating on an unpredictable schedule
A delayed customs clearance is an excursion in waiting. Without a continuous trip record, the receiving QA team has to decide on faith.
Engineered for this, specifically
Each point below maps to a documented platform behaviour — not a marketing promise.
Logger outside, probe inside — by design
ABH-100-D keeps the instrument, battery and indicator at ambient and runs a Class-A PT100 immersion probe (−50 to +200 °C, ±0.15 °C at 0 °C, 316L sheath, IP68 tip) to the measuring point inside the chest.
Four probed positions for a mapped ULT bank
ABH-300 carries four PT100 channels on one timebase, so a large chest or a row of freezers is mapped and monitored with one instrument, one clock and one audit record.
A trip report the recipient can open on any PC
Plug an offline logger into a laptop and it enumerates a FAT16 drive holding README.TXT, DATA.CSV and an ECDSA P-256-signed REPORT.PDF. No installer, no account, no dependency on the shipper's software — a self-verifying record.
Memory sized for the whole study
16 MB of flash holds up to 409,600 CRC-checked readings alongside a separate never-erased audit region, so a multi-week qualification at a short sample interval fits without wrapping the buffer.
Calibration tracked per probe
Each probe's channel template is written into the logger's ID EEPROM, and NIST-traceable certificates, due dates and reminders are tracked per probe — with calibration status carried into every report.
The ABH loggers for this job
Abhilekh runs its own logger line end to end — one manufacturer owns the chain from probe accuracy to the signed record.
- ▸PRB-PT100-3W — Class-A immersion probe, −50 to +200 °C, 316L sheath
The ABH line is at the design-frozen, pre-production stage. Every battery-life, drop, thermal and IP figure is a calculated or simulated design estimate, and the regulatory marks referenced on this site are a certification roadmap — not held certificates.
Questions, answered
Other environments we monitor
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