Essentia / Devices / Holter

Device Lab 40

Holter

Writes every sample of every channel for the whole ordered duration into a linear log. Nothing is selected, so nothing is discarded, and every later decision can be re-argued from the record itself.

Also called: Holter Monitor, Ambulatory Ecg. Arabic: جهاز هولتر. Device Lab 40 of 69 in BMEssentia Medical City, 2 configurations.

Overview: the configurations

How it works: the main parts

What each part does, from the Holter lessons in the 3D Device Lab.

Pre-gelled disposable electrode patch

A disc of closed-cell foam forty millimetres across with a twenty-millimetre window of wet gel in the middle of it, stuck to the chest and expected to stay there for two to fourteen days. Five of them are applied in the fitting room in about four minutes, and then nobody touches them again until the recorder comes back.

Conductive hydrogel column

A column of conductive hydrogel one millimetre thick and twenty millimetres across, sitting between the sintered pellet and the outer skin. It is mostly water with mobile ions in it, and it is the part of this device with a shelf life measured in the same units as the recording.

Sintered silver / silver-chloride pellet

A sintered disc of silver and silver chloride, eight millimetres across and just over a millimetre thick, recessed into the foam above the gel. It is the point at which the recording stops being ionic and starts being electronic, and it is chosen for what it does not do.

Stud and socket lead attachment

A four-millimetre stud pressed into the back of the pellet and a sprung socket on the end of the lead wire that clicks onto it. It is the only joint in the signal path that a patient can undo, and it is the only one they can accidentally undo.

Shielded patient lead wire

A shielded wire seven tenths of a millimetre in radius and a metre long, running from the snap on the chest to the yoke on the recorder. There are five of them and they spend two to fourteen days being bent by a person who is asleep for a third of it.

Patient cable yoke and recorder plug

A small moulded block where five lead wires meet one keyed plug, sitting on the top edge of the recorder. It is the single point through which every channel passes, and the only part of the patient side a patient is told they may unplug.

Input protection and defibrillation network

A set of series resistors, one per input, and two clamp arrays, sitting on the board within a few millimetres of the patient socket. It is there so that an energy the recorder was not designed for does not reach the amplifier, and so that the recorder does not become a path it should not be.

Instrumentation amplifier stage

The differential front end, a small package inside a soldered shield can, with its gain resistor beside it. It takes the difference between two electrodes and makes it large enough for a converter to see.

Common faults and what to check

Most reported device problems (FDA MAUDE)

Raw counts of adverse event reports for this device type (FDA product code MWJ, MLO, DSH), all years. Not adjusted for the number of units in use, so they show what gets reported, not failure rates. Report text is never copied.

Planned maintenance checks

From the BMEssentia procedure library: every 12 months, about 30 minutes, electrical class II, applied part type CF.

Test instruments: ECG simulator; Electrical safety analyser.

Recent FDA recalls

From the FDA recall database (openFDA), newest first, imported 2026-10-22. 7 recalls on record for this device type. Recall text is the FDA's public text; each recall links to the official record.

Learn it, see it in 3D, ask about it

• Ask Essentia about the Holter: answers from named sources, with the device open in its 3D Device Lab beside the answer.
• The Holter on the BMEssentia Platform: the Device Library course, 13 sections from physics to maintenance.
• BMEssentia Medical City: Device Lab 40, the Holter fully assembled in 3D, with lab tasks and the simulations.

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