Common Design

Sensors and Signals

Qameleon products are designed to evaluate the performance of the equipment they are connected to. The units should not interfere with the underlying devices. The best way to accomplish this objective is to use independent sensors that are installed separately without extensive modification to the equipment.. However, this is not always possible. For example, measuring the fluid level in a tank may require expensive installation. In this case, the Qameleon unit is connected in parallel with the control system to get raw signals from the existing sensors. Additional devices would be used to prevent interference with the equipment’s control system.

All Qameleon hardware units include similar interfaces for connecting sensors.

Two RS232 serial ports for connecting to external devices. An optional RS485 adapter is available.
Digital Inputs
Eight  optically-isolated digital inputs can be used to receive signals from switches and other instruments. Digital inputs are sampled at 1 mSec intervals.
Analog Inputs
Eight analog inputs measure voltages from sensors. They measure 0-5 VDC, with 12 bits of resolution. External components can be used to measure higher voltages or current. Analog inputs are sampled at 1 mSec intervals.
An external I2C interface provides high-speed connection with special-purpose sensors. The sample rate is determined by the individual devices.

A variety of sensors have been used with Qameleon units to measure physical properties. Commercial Off-the-Shelf sensors are preferred. We have also designed speciallized devices when suitable devices do not exist. Some of these sensors are described here.


A commercial remote GPS receiver is used to get accurate time information, as well as location. These receivers have long cables allowing the Qameleon unit to be located in an inaccessible location, such as a manhole, while keeping the receiver above ground. It uses a serial port. The receiver also provides a pulse-per-second dgital signal allowing multiple Qameleon units to synchronize their clocks with the GPS time.

Variable Frequency Drives

Large motors often utilize variable frequency drives to control their startup and shutdown rates. VFDs usually provide a serial port to read the status and error codes. We have interfaced to several VFDs using the ModBus protocol. Our software can be configured to work with other VFDs.

Power Monitors

Large facilities, like pump stations often have a power panel that controls the entire station. A power quality meter is often installed which provides measurements of the station voltage, current, and power. These measurements can be accessed using analog inputs or serial ports with the ModBus protocol. One of our implementations uses ModBus to set the time in the quality monitor to coincide with the GPS time in the SpikeWatcher unit.

Magnetic Relay Sensor

Control systems use a lot of relays. In order to avoid hardwiring to the control, we developed very sensitive magnetic sensors that are capable of detecting the magnetic field of the relay coil. These sensors are temporarily fastened near the relay coil and connected to digital inputs on the SpikeWatcher unit.

Combination Remote Sensor

Sometimes it  is necessary to measure properties of devices that are in tight locations. This may be the position of a door operator in an elevator or the valve position in a fluid system. This version of our remote sensor contains a color sensor, a proximity sensor, and a barometric pressure sensor. It connects to the SpikeWatcher unit using the external I2C interface.

Pressure Transducers

Off-the-Shelf pressure sensors are used for monitoring fluid systems. These are available in many different pressure ranges. In many cases, these are combination sensors which measure both positive pressures and vacuum. This makes them ideal for detecting transient pressures. We use sensors from different manufacturers depending on the needed configuration, such as submersible and explosion proof. These use the analog inputs of the SpikeWatcher unit.

Electrical Current Sensors

SpikeWatcher systems are often used to measure energy usage. Clamp-on sensors are used to avoid direct connection with the controller and to make installation easy. They are available in different current ranges. These use the analog inputs of the SpikeWatcher unit.

Temperature Sensors

Different types of temperature sensors can be used with the SpikeWatcher units. High temperatures can be measured with thermocouples, and silicon sensors can be used for lower temperature ranges. These are connected using the analog inputs.