Mercutech Electronic Product Development
applying excellent electronic engineering


Some Products developed by Mercutech

(the better ones from the years of design and development,
most were originally intended for niche applications)

Earth and Cable Monitor
(sales contact:
JoJen supplies)

For electrical safety as well as loss control: detecting damage to Earth or Neutral conductors.
This unit monitors the resistance of a wire in a circuit, e.g. an earth wire or the Neutral.
Resistance range: 0 – 5 Ohms.

A split-core toroid is clamped around a conductor (eg. an earth wire) for monitoring the resistance of the circuit in which the wire is running.
A change in this measurement will trigger an alert.
A 50Hz current can also be detected to trigger an output, indicating an earth fault current or overcurrent.
It has two inputs for connecting contacts, eg. door switches or IR detectors.
An external rechargeable battery can be connected to provide some hours of operation during a power failure.
Connects to 110 - 220V single phase AC supply

The output is a N/O or N/C relay contact and it can send SMS's or misscalls


Earth Wire Monitor
(sales contact: JoJen supplies)

Earth Wire Monitor for installation at load side (e.g. motor) where there is no Neutral

Monitors the resistance of the earth wire as measured between the Earth wire and the transformer star point.
Resistance range: 150 – 500 Ohms.

Rugged and all-solid state.Suitable for 380 - 525V systems.
Trip point (Ohms) as requested in the above range.
Typical trip delay is 5 sec.s, can be made for other voltages and trip delays.

Earth Wire Monitor

(TWR = Transformer Watchdog Relay)
(sales contact: JoJen supplies)

Each trip source has it's own indicator blinking for 2-3- days with no power.
One N/O solid state contact for the shunt trip coil, operated by:

- Resistance of Neutral-Earth Resistor (NER) out of limits
- Earth Fault current  in NER exceeding limit
- Any one of 4 inputs activated, e.g. from other protection Relays
   like over-temperature, PRV, Buchholz, flash detector

Supply: 110V ac or as otherwise specified
Resistance measurement range: 0 - 150 Ohms
Typical Resistance limits: 63 Ohms +-15%, typ.delay: 7 sec
Typical trip delay on Earth Fault current: 2.5 sec
Trip delay for each of the four 110V inputs: 100 msec
Internal watchdog to trip the output on internal failure (0.5 sec)

Values other than those above can be supplied

(sales contact: JoJen supplies)
Motor start-up Sequence and Vigilance Controller
intended for safety on winch motors, underground motors etc.


for monitor & control through SMS's and miss-calls using your cellphone.
Just needs your SIM card and off you go.

 basic celtifier - big electronic product development

Wireless proximity detection
used for collision avoidance in underground locos
working on 433MHz

Bayete's product RF receiver


Digital Timer with DIP switches
settable range: 0.25 – 63.75 seconds
  in steps of 0.25 sec
(longer times are supplied on request)

70x50x23mm box
70 x 50 x 23mm

USB-RS232-I2C-PIC programmer Adaptor box

70 x 50 x 23mm

low cost Fluid immersion sensor

70 x 50 x 23mm

Telephone recording interface
detects on/off-hook,
digitises sound and transmits WAV packets to PC via USB

Telephone digitiser
70 x 50 x 23mm

Spinning wheel with 20 lights
and controller

for probability based on programmed probablilities.
Each number appears at random intervals but has a predefined number of hits out of a specified number (300 in this example)

 spinning wheel of 20 lights<-heart of electronic products

Podium display with response buttons
and controller

Each display box has a thumbwheel number entry associated with it,
after setting up a button is pressed to display the number

 Podium displays

EDMU: Energy Display and Management Unit

For installation in homes to manage peak consumption
by warning, disconnecting and reconnecting load circuits
with internal and external data links




 Affiliate Products


passive metal detector
Portable, lightweight and battery operated, fold-up model available.
Based on a sensor module (Mercutech) which monitors small changes in the earth's magnetic field.
(See article on microvolt amplilfier)

Contact Roteck

 magnetic sensor module ->metal detector frame

Dual beam for outside use
Developed, manufactured and sold by
MJR: contact Martin at 082 3902448

 dual IR beam

 Legacy Designs


Automated PC controlled test station with
- 2 serial communication links
- controlled 3-phase current oputput
- cotnrolled 3-phase voltages
- manual override

 Automated test station with current control & 3-phase

Multifunction Earth Fault Protection Relay
with SCADA Comm.s (Profibus)


Nurse call system with mimic panel
for 80 bed units on serial bus,
full event records in non-volatile memory

 Nurse call system

Socket Tester
for testing the integrity and safety of South African power outlets

(being redesigned for ruggedness)

 Socket tester  leaflet

DC earth leakage monitor
2mA resolution on 50mA range.
Using magnetic toroids,
based on core balance and BH nonlinearity


 DC earth leakage monitor

Test station
for Eskom's Remote Terminal Units
in their Acquisition and Telecontrol system.

 RTU test station at IST

Field test unit, based on the 8751, C and Assembler
for a missile launcher including optical, RF detectors and gyros

 missile launcher tester

Motor protection Relay based on analog simulation of an accurate thermal model of an induction motor.


Passive earth fault protection Relay
(20-2000mA-ac, 250-2500msec) for high-voltage installations
(Erich's first patent)

(contact JoJen supplies for the ERCM)



To develop high-tech products exploiting a lifetime of experience. Thereby contributing to our technological and information age.


Key Benefits of Engineering Outsourcing

  • Reduce or eliminate fixed expense on R&D 
  • Expand your resources as and when needed, without personnell turnover
  • Add expertise to your development team
  • Supplement your own resources to relieve pressure on critical path tasks
  • Free your internal resources for tasks at hand
  • Reduce time-to-market

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Creative ideas
concept in the clouds
conceptual product

circuit design,
PCB layout,
and cost control

PCB assembly
testing and debugging