Portable High-Accuracy Thermal Measurement System

EMP Designs was approached to develop the electronics for a portable measurement device requiring extremely precise control of both energy delivery and temperature measurement.

The application relied on a small heating element being driven with a carefully controlled amount of electrical energy. Once heated, the system then needed to accurately monitor how the temperature changed over time.

The resulting temperature-decay data could then be passed to the client's proprietary algorithms, allowing them to interpret the characteristics of the material being tested.

While the principle sounds straightforward, achieving the required accuracy in a compact, battery-powered device presented several significant engineering challenges.

Precisely Controlling the Energy

The first challenge was controlling the heating element.

Rather than simply applying power for a fixed period, the device needed to deliver a very accurately controlled quantity of energyto the heater.

Small variations in current, voltage or timing could affect the starting temperature and therefore influence the subsequent measurement.

We therefore developed electronics capable of controlling the heating cycle accurately and repeatably, ensuring that each measurement began from a known and controlled energy input.

Measuring the Temperature Decay

Once the heating cycle had finished, the next stage was to monitor the temperature as it naturally decayed.

The system needed to capture this change with sufficient accuracy and at adjustable measurement intervals, producing a detailed temperature profile over time.

This data could then be processed into a format suitable for the client's own analysis software and proprietary algorithms.

Effectively, the electronics needed to perform two quite different tasks extremely well:

deliver a precisely controlled burst of energy, and then immediately become a high-accuracy measurement system.

Balancing those requirements within one compact design formed a significant part of the development work.

Designed for Long-Term Battery Operation

The device also needed to operate remotely for extended periods.

In some applications, measurements could be taken over weeks or potentially months, making power consumption an important part of the design.

It wasn't enough simply to optimise the electronics while they were active. We also needed to minimise the amount of power consumed between measurements.

Considerable development therefore went into:

• reducing sleep-state power consumption

• managing the system's different operating modes

• optimising when individual circuits were powered

• maintaining measurement accuracy while reducing energy consumption

• managing data storage and communications efficiently

The objective was to allow the device to perform numerous measurement cycles over a long period without requiring frequent battery charging or replacement.

Low-Power Wireless Data Transfer

The system can store measurement data internally, but there was also a requirement to transfer collected information to a computer.

Wireless communication can be one of the largest power consumers in a battery-operated product, so we investigated ways of using newer Wi-Fi communication methods while minimising the amount of time the radio system needed to remain active.

By carefully controlling when communications were enabled, data could be transferred while keeping the overall energy consumption of the device low.

Turning an Experimental Requirement Into Portable Electronics

The result was a compact electronic platform capable of combining:

• highly controlled energy delivery

• accurate temperature measurement

• adjustable sampling periods

• long-term data logging

• internal data storage

• wireless transfer to a computer

• low sleep-current operation

• extended battery-powered deployment

The project required development across analogue measurement, precision power control, embedded firmware, power management, data acquisition and wireless communications.

It is a good example of the type of work we undertake at EMP Designs: taking a specialist measurement requirement and developing the electronics and embedded systems necessary to turn it into a practical, portable device.