EMS Hardware Development

About this page

This page was written by the New Horizons engineering team, which operated until December 2025. First-person references ("we", "our") are the original authors'. A number of those authors are now working with Phoenix GH, which maintains this material and stands behind it. Questions and comments are welcome — please get in touch.

Last update: March 18, 2025

Overview

Following the publication of the WHO PQS Equipment Monitoring System (EMS) specifications, New Horizons developed an EMS level-1 logger as a demonstration product and an opportunity to learn. This page provides links to public assets that we developed during the development of this logger.

USB compatibility in EMS devices

During this process, we encountered a variety of USB-related challenges—both in our own design and when evaluating pre-release samples from third-party suppliers. We have documented our experiences and recommendations on the first page linked below, with the hope that it will help manufacturers build more reliable EMS loggers.

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     USB implementation guidance

Demo EMS logger hardware and firmware

We are also sharing details of the logger hardware and key parts of the logger source code in the hope that it will help others developing EMS hardware and firmware. More details, including a link to download firmware, are provided in the page below.

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     Demonstration EMS logger

JSON Schemas for custom data objects

EMS allows manufacturers to define custom data objects, but they must document them with publicly available schemas. This page explains ways to create such a schema.

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     JSON Schemas for custom data objects