Part Details for AD568 by Analog Devices Inc

The AD5750/AD5750-1/AD5750-2 are single-channel, low cost, precision voltage/current output drivers developed to meet the requirements of industrial process control applications. The output voltage range can be programmed for the standard output ranges for PLC and DCS applications: 0 V to 5 V, 0 V to 10 V, −5 V to +5 V, and −10 V to +10 V. A 20% overrange setting is also provided for the standard ranges, giving the following options: 0 V to +6 V, 0 V to +12 V, −6 V to +6 V, and −12 V to +12 V.

The CN-0508 provides a low cost, adjustable power solution with performance comparable to high-performance commercial power supplies.

The total dissolved solids (TDS) present in a water system is composed of inorganic salts and small amounts of organic matter that are dissolved in water, and is an important measure of water quality. TDS can be derived from the electrical conductivity (or conductivity) of the solution by a factor dependent on the properties, temperature and, number of ions present. By measuring the conductivity of the solution, determining the TDS of the system is faster, economical, and less complicated in contrast to the more accurate gravimetric method. The latter method involves evaporating the water and weighing the residue, which is applicable in laboratory settings but impractical in the field.<p>This circuit is a TDS measurement system based on the conductivity of the solution. This design uses a combination of components that allow for single-supply operation, which minimize circuit complexity, making this suitable for low-power and portable instrument applications.<p>The simplest method of measuring the conductivity of the solution uses a 2-wire conductivity cell. Conductivity measurements require temperature compensation for measurements taken at temperatures other than 25˚C (or other reference temperature). This system can reference the conductivity measurement to room temperature using either a 100 Ω or 1000 Ω, 2-wire resistance temperature device (RTD) and can accommodate 2-wire conductivity cells of various cell constants and operating parameters.<p>The capacitance and polarization effects of the electrodes in the conductivity cell require that the excitation signal be a bipolar square wave with a sufficiently high frequency to reduce polarization effects but also with sufficiently long periods to reduce capacitance effects. To avoid damaging the conductivity electrodes, the signal must have a very low to zero dc offset and magnitude.<p>The circuit can measure the range of conductivity values from 1 µS to 0.1 S. A multiplexer switches between seven precision resistors of different values to set the gain when measuring the conductivity probe signal. The system can automatically determine the gain setting of the conductivity measurement through an auto-ranging procedure implemented in software. The system can also be calibrated in the high conductivity range to increase its accuracy.