425-252-115 - Calex Mfg. Co. Inc.

Models 415-215 and 425-252 Voltsensors

Manufacturing Company, Inc.

• Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com

Description

For process control systems and manufacturing test

equipment, here is a complete Voltsensor system in a single

package—no external components needed, just connect it to

115 VAC for power. These modules contain a DC power

supply, reference voltage, adjustable setpoint, and the output

is a DPDT relay. A LED indicator shows output status. The

relay changes state as the DC input voltage varies around the

set point. Because the unit has its own built-in power supply

and the output is a set of relay contacts, you can apply floating

inputs with voltages of up to 1500V above the AC line neutral.

This isolation makes it feasible to connect ungrounded

thermocouples directly to the amplifier inputs.

Model 425-252

Model 425-252 has a trip range of -14VDC to +14VDC relative

to the module common. Hysteresis is adjustable from 50 mV

to 1 Volt, and sensitivity is 1 mV, so this module should be

used on signals with several volts of amplitude. The input

signal can be floating and the isolation from AC neutral is 500

megohm paralleled by 250 pF. With the latching jumper

removed, the module will latch when the relay goes to the

energized state. The latching state is broken by interrupting

the AC line voltage to the module or momentarily reconnecting

the latch jumper.

Turning the set point adjustment potentiometer clockwise

makes the set point more positive. Turning the hysteresis

adjustment potentiometer clockwise increases the voltage

difference between pull in and drop out.

FIGURE 1-a. Simplified Block Diagram, Model 425-252

Turning the set point adjustment potentiometer clockwise makes

the set point more positive. Turning the hysteresis adjustment

potentiometer clockwise increases the voltage difference between

pull in and drop out.

The modules are epoxy potted for ruggedness and they can

operate over a temperature range of 0° to 50°C. The inputs are

protected against damage due to overvoltage. When you

need an alarm or control circuit in a rugged industrial

environment where ±15VDC power is not readily available,

then these Voltsensors are an excellent choice. Small process

control systems involving temperature control, weighing, and

monitoring can easily be designed using these reliable, low-

cost modules. No complicated wiring, simply connect input

and output with a screwdriver and the control system is ready

to operate.

Model 415-215

Model 415-215 is designed to accept low-level signals, such

as strain-gage bridge outputs and floating thermocouple

signals. Trip point range is ±100mV relative to the module

common. The input signal can have up to ±6V common-mode

voltage relative to module common, and all three input leads

are isolated from ground (500 megohm in parallel with 200

pF). Floating inputs with voltages up to 1500V above the AC

line neutral can be accommodated by this module. Latching

and adjustable hysteresis from 50 µV to 1 mV operate in the

same manner as the 425-252.

FIGURE 1-b. Simplified Block Diagram, Model 415-215

Models 415-215 and 425-252 Voltsensors

Manufacturing Company, Inc.

• Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com

Specifications

NOTE: With latching option, relay latched in energized state. FIGURE 2. Output Logic

Operation

The Industrial Voltsensors consist of a DC power supply,

reference voltage, adjustable set-point comparator, and DPDT

relay-all in a rugged epoxy-potted module. As shown in

Figures 1-a and 1-b, 115VAC is rectified to power the

comparator and provide a reference voltage for the set point.

This set point is adjustable by means of a multi-turn, high-

resolution cermet pot located next to the barrier strip. The

comparator consists of a differential amplifier (415-215 only),

summing network, buffer amplifier, DC amplifier, trigger circuit

and an emitter follower which provides the necessary output

to drive the DPDT relay. An LED indicates when the relay is

energized. Output logic of the Models 425-252 and 415-215

is shown in Figure 2. The relay is energized in both units when

the input voltage is more positive than the set voltage. Fail-

safe operation is achieved by operating the unit with the relay

normally energized. This way a change in relay state will

occur if the input voltage drops below the set voltage or if

Model 425-252 Operation Model 415-215 Operation

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115VAC power is suddenly lost. By exchanging the input

signal leads, the output logic can be reversed on the 425-252.

The relay would then be energized when the input voltage is

more negative than the set voltage. The module common is

isolated from ground so either signal input can be designated

as the system common.

Latching

Both models can be operated as latching units. When the

input voltage is more positive than the set voltage for no less

than 10msec the relay will latch in the energized state. The

relay will remain latched even if the output voltage becomes

more negative than the set voltage. To unlatch the relay, the

AC line voltage to the unit must be interrupted for at least

100msec or the jumper reconnected, and the input voltage

must be more negative than the set voltage. An external

switch can be used in place of the latch jumper for ease of

resetting.

Models 415-215 and 425-252 Voltsensors

Manufacturing Company, Inc.

• Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com

ON/OFF Differential (Hysteresis)

Both units have adjustable ON/OFF differential (hysteresis or

dead band). This is the difference between the voltage at

which the unit switches on with a positive going signal and the

voltage at which the unit switches off with the same signal

going in the opposite direction back through the set point. The

hysteresis is adjustable from 50 mV to 1 V on the Model 425-

252 and 50 µV to 1 mV on the Model 415-215. Increasing the

hysteresis (turning the pot clockwise) will provide improved

noise immunity at the expense of lesser sensitivity.

Applications

FIGURE 3.

Two Models, 425-252, Connected as a Single Input, Dual Set Point,

Dual Output Window Comparator.

FIGURE 4.

Model 415-215 Connected as a Bridge Amplifier and Comparator.

Installation

All connections can be made to the terminal strips with a

screwdriver. Mounting hardware is supplied with each unit.

This hardware consists of two #10-32, 3-inch long screws and

mating #10-32 nuts and washers.

To adjust the set point, an input signal is connected to the

Voltsensor. The input is then adjusted to the desired set point

voltage and the Voltsensor pot is turned until the relay

changes state (LED goes on or off).

Input Impedance

Differential Input Impedance is defined as the impedance

between the two input terminals. Common-Mode Input

Impedance, in the case of the Industrial Voltsensors, is

defined as the impedance between the shorted input terminals

and AC input neutral. This impedance is essentially the power

transformer impedance, as shown in Figure 1. Because of the

built-in power supply and relay output, floating inputs with

voltages up to 1500V above or below the AC line neutral can

be accommodated by this module.

Mechanical Specifications

Mounting hardware and latch jumpers are supplied with each module.

Inputs are exchanged to obtain reverse output logic.

Model 425-252

Model 415-215