General Characteristics

Vl 92 has been designed to fulfil any requirement for the visualization of signals coming from measuring instruments, especially in the water treatment field. The whole line made available covers any possible application, from small-size household plants to medium and large-size industrial ones. The constructional criteria have been such as to ensure maximum reliability in a number of operating conditions. Besides its displaying function, Vl 92 can act as a Proportional Controller (IF) able to control a metering pump with automatic setting of flowrate value and 0-100 % proportional range of input signal. A classical example of a water treatment process chain is that in which a flowmeter delivers a signal to the Vl 92 which processes it through the proportional function. The thus processed signal is picked up by the self-regulator which converts it into a mechanical movement which, in turn, changes the stroke of the crank mechanism to regulate the flowrate of the metering pump PD. The feedback signal emitted by the self-regulator AR 91, communicates the Vl 92 its actual reading and, consequently the one of the Metering Pump PD, the latter data being visualized on the display.

General Characteristics

Possible types of regulations: - ON-OFF - Pl (proportional and integral) - PIQ (proportional, integral, and directly proportional to flowrate). The PIQ adjustment represents an important novelty inasmuch as it allows an immediate intervention to be made for the intake of the chemicals upon any change of liquid flowrate, without waiting for the analyzer's return signal. A metering can also be made proportional only to the flowrate (IF). Moreover, by associating the operating threshold with one of the two other thresholds (MAX or MIN), a hysteresis-based ON-OFF type adjustment may be made as well. The proportional parameter "P" may range from 0% fo 400% and the integration time "I" from 1 and 20 minutes. The flowrate parameter "Q" is directly related to the metering level. The regulation is typically performed by using the 4 -:20 mA analog output which governs the self-regulating metering pump (4 mA = 0% flowrate; 20 mA = 100% flowrate), but the ON-OFF output may be used as well, which allows a PWM to be carried out over a time which is generally of 60 seconds. The calibration of the unit can be performed by entering data relevant to two characteristic points of the measurement range. Should these data be not easily available, the use of an automatic calibration system based on stored-in-memory average parameters would be in order.

General characteristics

Possible types of regulations: - ON-OFF - Pl (proportional and integral) - PIQ (proportional, integral, and directly proportional to flowrate). The PIQ adjustment represents an important novelty inasmuch as it allows an immediate intervention to be made for the intake of the chemicals upon any change of liquid flowrate, without waiting for the analyzer's return signal. A metering can also be made proportional only to the flowrate (IF). Moreover, by associating the operating threshold with one of the two other thresholds (MAX or MIN), a hysteresis-based ON-OFF type adjustment may be made as well. The proportional parameter "P" may range from 0% fo 400% and the integration time "I" from 1 and 20 minutes. The flowrate parameter "Q" is directly related to the metering level. The regulation is typically performed by using the 4 -:20 mA analog output which governs the self-regulating metering pump (4 mA = 0% flowrate; 20 mA = 100% flowrate), but the ON-OFF output may be used as well, which allows a PWM* to be carried out over a time which is generally of 60 seconds. The calibration of the unit can be performed by entering data relevant to two characteristic points of the measurement range. Should these data be not easily available, the use of an automatic calibration system based on stored-in-memory average parameters would be in order. A little adjustment is also possible upon only one measuring point.

The major feature of the SA probes lies in the integration of the electrode- holder and the signal amplifier/ transmitter so as to offer the following advantages:

• easy installation
• long distance from the control instrument (max output resistance 200 ohms).
• 12 V d.c. power supply
• 4-20 mA output signal

The probes of Sodi Scientifica can accommodate electrodes for measurements of pH, Redox, conductivity and dissolved oxygen. Each measure (Redox excluded) can be temperature-compensated with no need for additional probes or electrodes. The calibration is carried out through the control instrument.

Probes Specifications

Runoff cell

Probe with signal amplifier