Models 940 and 945 DC Transmitters Features Description n 4 to 20mA Output n 0 to +10V Input - Model 940 n 0 to 50 mV Input - Model 945 n 700 Volts DC Isolation n PC Board Mount Modular Design for OEM Applications The CALEX Model 940 and 945 are fully DC isolated voltage to current transmitters. They are ideal for eliminating ground loops and common mode problems in data acquisition and process control systems. The 20 Volt maximum output compliance voltage allows a loop resistance of up to 1000 ohms. The isolation input to output is 700 Volts DC. The input and output are also isolated from the unregulated +14 to +16 VDC power source. n Convenient Mounting Kit Available for End User Applications n Powered by 14 to 16 Volts n 24 VDC Operation Available Model 940 and 945 Block Diagram 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 1 CALEX FaxFACTS: 319 1997 A Models 940 and 945 DC Transmitters Specifications Input Voltage Resistance Operation 940 945 0 to +10 Volts 0 to 50 mV 10 megohm minimum Output Current 4 to 20 mA Load Resistance For 4 to 20 mA operation, a 200 ohm external cermet potentiometer is required to set 4 mA Zero Current. Connect the wiper to pins 6 and 8. Connect one end terminal to pin 7 with a 604 ohm 1% resistor in series. Connect the other end terminal to pin 8. Tie pin 4 to pin 3. Reference Model 940 Block Diagram. 0 to 1000 ohm Compliance 20 Volts maximum Frequency Response Rise Time 0.9 ms Settling Time to 0.1% Noise 2.5 ms 1 mA P-P 50 mA P-P 1 kHz bw 20 MHz bw Power Supply Sensitivity Zero S pan Accuracy @ 25°C 5 mA/ Volt 0.005%/Volt 0.1% of Full Scale Linearity 0.05% of Full Scale Temperature Coefficient Zero S pan Isolation - Input to Output Mechanical Specifications 400 Hz @ 3 dB 0 to 55°C 0.0035%/°C of Full Scale 0.0035%/°C of Full Scale 700 Volts DC or Power Supply 25 pF Capacitance Pow er Requirements DC Voltage Current 14 to 16 Volts DC 125 mA Zero Set BOTTOM VIEW External Cermet Potentiometer Required to set 4mA Zero current. External Pot may be used to set output current 0 to 20mA. Environment P a cka g e Size (inches) 2" x 2" x 0.6" 2.5 oz. 1 2 3 4 5 6 7 8 9 10 +INPUT -INPUT RETURN RETURN CURRENT OUTPUT Reference Model 940/945 Block Diagram Reference Model 940/945 Block Diagram Reference Model 940/945 Block Diagram -DC POWER +DC POWER A 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 2 CALEX FaxFACTS: 319 1997 Weight Pin Assignments Encapsulated Plastic Module Models 940 and 945 DC Transmitters Mounting Kit The MK940 mounting kit is an optional printed circuit board that provides the necessary potentiometers and a connector for a complete turnkey system. The 940/MK940, when ordered as a combination, is shipped from the factory configured as a 0 to +10 Volt input, 4 to 20mA output, isolated transmitter. The 945/MK940, when ordered as a combination, is shipped from the factory configured as a 0 to 50 mV input, 4 to 20 mA output, isolated transmitter. Note in the schematic, Figure 1, that C1, R1, R2, R3, and R5 are included on the board. The other designated components are user supplied for other applications. Also note that R8 through R11 are not connected to the rest of the circuit. For 24 VDC operation, add a “-24” to the MK940, i.e. 945/MK94024 Figure 2 shows the outline of the MK940 card and the lettered pin assignments. The card includes a Model 015 connector with edge guides and has eyelets for soldering wires. The components described as jumpers are wire connections although they have a ceramic body the size of a ¼W resistor. NOTE: C1, R1, R2, R3, R5 ARE INCLUDED. ALL OTHER COMPONENTS ARE USER SUPPLIED FOR SPECIFIC APPLICATIONS. FIGURE 1. MK940 Schematic A FIGURE 2. MK940 Card 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 3 CALEX FaxFACTS: 319 1997 Model 940/945 Models 940 and 945 DC Transmitters Applications The 940/MK940 may be configured for 4 to 20mA output, as a constant current source, as a 0 to 1mA current source, 0 to 5V output, voltage input and 1 to 5V output, or an isolated voltage input and 4 to 20V output with a single pole 10Hz input filter. Figures 3 through 8 illustrate these configurations with the Model 940/945 and MK940 mounting kit. The R-numbers refer to locations labeled on the MK940. All fixed value resistors should be metal film 1% type. Where a potentiometer is shown, use a multiturn trim pot with a CERMET resistance element. The hole pattern is for industry standard potentiometers such as Bourns “3006Y”, Spectrol “43”, and Beckman “89” series. MK940 Application Isolated 0 to 20mA Output NOTE: R6 IS A 1% METAL FILM 1/4 W RESISTOR. ZERO CURRENT MAY BE 100µA FIGURE 3. Shows an isolated 0 to 20mA current loop. In this application the ZERO pot is not used and is replaced by a wire jumper. R6 parallels an internal 50 ohm resistor to change the scale factor. The zero current may be from 10nA to 100µA. Zero current must be checked with a short between pins F and H, or 0 Volts input. Do not leave the input open. MK940 Application Isolated Constant Current Source FIGURE 4. Is a potentiometer adjust 0 to 20mA constant current source which is isolated from the power supply. The jumper in place of R4 ensures that the input is zero volts. Do not apply any control voltage to the input. The output will drive zero to 1000 ohms with a 15 volt power supply. 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 4 CALEX FaxFACTS: 319 1997 A Models 940 and 945 DC Transmitters MK940 Application Isolated 0 to 1mA Current Source NOTE: R5 IS A 1% METAL FILM 1/4 W RESISTOR. FIGURE 5. Zero to 1mA current source. The load resistance may be 0 to 20,000 ohms. Other values of full scale current may be set by changing R5. The maximum output current is determined by 0.8V/(R5+50) and is limited to 20 mA. MK940 Application Isolated 0 to 5 Volts Out A R6 IS A 1% METAL FILM 1/4 W RESISTOR. FIGURE 6. Shows a voltage to voltage transmitter. Note that this configuration will have a 249 ohm output source resistance which will produce an error of 2.5% if driving a 10,000 ohm load or 0.25% if driving a 100,000 ohm load. R6 parallels the internal 50 ohms to produce 20mA output with full scale input. There will be 0.8 Volts between pins 7 and 4 with full scale input. 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 5 CALEX FaxFACTS: 319 1997 NOTE: Models 940 and 945 DC Transmitters MK940 Application Isolated Voltage In - 1 to 5 Volts Out NOTE: R13 IS A 1% METAL FILM 1/4 W RESISTOR. FIGURE 7. Is similar to Figure 6 except R1 and R2 are used to set 4mA, or 1 Volt at the output with zero Volts input. Also R5 is zero ohms. MK940 Application Isolated Voltage In - 4 to 20 Volts Out with Single Pole 10Hz Input Filter A 1997 R13 IS A 1% METAL FILM 1 W RESISTOR. FREQUENCY LIMIT - INPUT FILTER DC TO 10 Hz BAND PASS FIGURE 8. Shows how to add a low pass filter at the input where the 400Hz bandpass may be too high and is causing noise problems. C4 should be a low dielectric absorption capacitor such as a X7R ceramic or a film capacitor. As discussed in Figure 6, R13 is the output source resistance and in this case would produce a 10% error when driving a 10,000 ohm load, and a 0.01% error when loaded by a 10 Megohm input digital voltmeter. 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 • Fax (510) 687-3333 Powered by ICminer.com Electronic-Library Service CopyRight 2003 http://www.calex.com 6 CALEX FaxFACTS: 319 NOTE: