The bench test [2]: Going loopy

Many security installer readers will be familiar with ACT Meters. Operating from Rainford in Merseyside, it has distributed a range of products for security industry professionals throughout the UK for more than twenty years, consisting of diagnostic tools and test equipment.

The Prove a Loop is a useful addition to the portfolio. Essentially a continuity testing tool, it uses wireless technology to enable one man to determine the efficacy of a troublesome alarm cable or device.

The kit is not sufficiently water proofed for external use (though it could certainly be used to establish SAB cable faults in dry weather ) and does not carry the European CE mark for electrical conformity.

Construction and design

Most installers will be familiar with the Check Mate tester, available from ACT for many years. It is a sophisticated wireless transmitter and receiver tool that gives break down engineers the ability to remotely read a multimeter, and in theory allows one man to diagnose a fault more swiftly and effectively by being 'in two places at once'.

An undoubtedly good idea, its widespread usage in the security industry has probably been hindered by the high price tag – currently a hefty £999 + VAT!

In essence, this kit is a cut down version of the Check Mate tester, giving an audible, variable tone in an earpiece to gain information pertaining to the resistance of the circuit under test. At a trade price of £189 + VAT, the Prove a Loop will be a welcome addition to the average installer's kit and could pay for itself in two or three call outs.

Each of the receiver and transmitter devices are light and portable due to their battery operation, and two 9 volt PP3 type batteries were provided with the kit. Also necessary for operation are a mono earpiece to connect to the receiver to 'read' the information, and a pair of (too) short plug-in leads to attach the transmitter to the suspicious item by means of mini crocodile clips. All of this is usefully housed in a tough plastic mini brief case, with a shaped foam liner to protect the equipment from the shock of being thrown into the back of a van.

Operation

The continuity of the cable and device under test is presented to the installer as an audible tone – through the earpiece – that varies in pitch relative to the resistance effectively being measured. It is a much more crude method than the precise digital output reading given by ACT's flagship tester, the Check Mate, but with some practice beforehand using known resistance values we were able to gain useful information with the Prove a Loop in a short time. At very high resistances the tone degenerates into a broken output that is still useful.

The receiver was found to have a maximum wireless range of around 80-90m, though this measurement was achieved in free space, and ACT Meters will readily admit that this can change dramatically inside a premises due to the fabric of the building construction.

Certainly the metalwork of a building is a known cause of attenuation of radio wave range at any frequency. It is worth noting that the earpiece sound quality started to degenerate after half that distance, as interference was introduced into the system, though the varying tone was still sufficiently audible to be useable.

Further thoughtful touches include a belt clip to hook on the receiver box, leaving the engineer with two free hands, and a rotary volume switch to up the level if the battery starts to run out of power.

Literature and support

The equipment is so simple and obvious in its operation that instructions are barely necessary. The technical literature is provided on a single A4 sheet and includes useful tips to demonstrate the Prove a Loop's versatility, including testing vibration sensors from outside the building (great idea) and tap testing surface cables to find suspicious high resistance problems.

We called ACT during working hours to check some technical issues. Unfortunately, top banana David Grant was unavailable on holiday, though another member of staff offered to find out the answer our question, which was subsequently resolved.

What the manufacturer says ...

This unit is a completely new way of testing security alarm systems using a pocket sized RF unit up to 100 meters. One engineer uses it, so there is no need for two engineers on a large system, to test and fault find commercial or domestic alarm faults.

The engineer will attach the transmitter, which transmits a fixed tone to the control panel, and then walk test the system with the receiver. This has an earpiece that enables the engineer to listen to the switch action of the system while listening to the tone.

Any variation in the tone cased by resistance, such as a dirty switch or broken cable, will denote an impending or actual fault. This saves time because the engineer does not have to continuously go back to the panel to check each switch action; he can walk test the whole system in one pass. This time saved is money saved and makes the engineer much more productive.

The benefits are many, providing an accurate single user, and the unit is able to locate faulty cables, connections and alarm detectors in real time, proving the circuit in a fraction of the normal time using a license-exempt radio link.