The holy grail of asset tracking tags could now be a reality

There are plenty of situations where the operator using a piece of equipment needs to know it’s been correctly tested, calibrated and serviced, to ensure it is both safe and fit for purpose.

The limitations of traditional asset tracking tags
Both goals can be achieved using readily available asset tracker tags, which attach to each item, incorporate a location sensor and some form of wireless communication technology, and store other vital information about the asset. This enables a central operations team to monitor where things are and flag when they need to be taken out of service for maintenance.

For anyone using the equipment, however, the data stored on the tag can only be accessed with the help of an additional device. This could be a specialist scanner or a smartphone, for example. But whatever it is, the individual has no way of knowing, at a glance, whether the equipment they’re about to use has been correctly calibrated or serviced. And if their reader device fails (perhaps because of a dead battery or not having a network connection) the operators would face the choice of delaying the job or using potentially defective or inaccurate equipment – the consequences of which could be severe.

The difficulty of adding a display
Adding an always-on status display to the asset tracking tag on the equipment is therefore highly desirable. However, traditional display technologies have rendered this impossible in most cases. A wireless device tag has a limited power budget and must operate for months, if not years, between battery changes. Thin-Film Transistor (TFT) Liquid-Crystal Displays (LCDs), for years the go to option for flat screens, are notoriously power hungry. Even a relatively small TFT LCD, left switched on, would wipe out a CR2032 coin cell battery in a few hours. To this day, this power challenge means most asset tracking tags have remained display less.

E-paper: the low-power alternative
This could be about to change, however. In situations where the content of the display only needs to change sporadically, e-paper displays (EPDs), as seen in many e-book readers, are significantly more power-efficient than TFT LCDs.

There are two main reasons why this is the case. Firstly, TFT LCDs require a backlight, where EPDs don’t. This is because the latter contain physical pigment particles, off which ambient light reflects to produce an image that’s visible to the eye.

Secondly, even to maintain a static image, TFT LCDs must refresh around 50 times per second. Every refresh requires energy, meaning TFT LCDs are constantly drawing on the battery. EPDs, on the other hand, only need to refresh when you change what’s on the display. Put another way, once you’ve got something showing on an EPD, keeping it there requires no power.

E-paper power usage vs TFT LCDs
To show just how transformative EPDs can be, imagine a two" display that needs to permanently show status information about a piece of equipment. Assume this information is updated remotely, six times per day.

A TFT LCD would consume around 30mA constantly, giving a daily power usage of 2,592,000 mAs or 720 mAh.

An optimised EPD would use 2.33mA per refresh, each taking 2.32 seconds, giving a total daily power use for six refreshes of 32.43mAs, or 0.01mAh.

Given that the only power source may be a 225mAh-capacity CR2032 coin cell battery, this example demonstrates why the TFT LCD isn’t a viable option. The EPD, however, would barely make any inroads at all into such a battery. As a result, tag manufacturers would be able to incorporate an EPD in their designs, without having to significantly compromise elsewhere to accommodate it in the power budget.

Transforming safety and efficiency
Adding a display to the tags that keep track of high-value assets would help improve efficiency and safety. By displaying details about the device, such as when it was last calibrated, or status information, such as ‘Faulty – please service’, anyone needing to use it would know whether it’s appropriate to do so – without having to reach for a separate device to access the information.

This would help operators work more quickly, while cutting down on the consequences of errors caused by the use of faulty or uncalibrated equipment.

EPDs and development kits are available off the shelf in small and large volumes from manufacturers such as Pervasive Displays. This gives product designers a low cost way of trialling the technology, along with the confidence that they can buy in bulk once their designs are proven.