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Both voltage and current outputs can also be controlled by a voltage source. A voltage of 0 to 5 volts programs the output voltage or current from zero to full scale. Voltage sources of more than 5 volts can be scaled down to the proper range. The following paragraphs discuss in greater detail the methods of remotely programming the output voltage or current using either a resistance or voltage input. Whichever method is used, the wires connecting the programming device must be shielded to reduce noise pickup. The outer shield of the cable should not be used as a conductor, and should be connected to ground at one end only. Although the following setup drawings (Figure 3-7 through 3-11) show the supply strapped for local sensing, analog programming and remote voltage sensing do not interact and may be used simultaneously. Constant Voltage Output, Resistance Control. The setup shown in Figure 3-7 allows the output voltage to be varied by using an external resistor to program the power supply. A programming resistor variable from 0 to 4000 ohms produces a proportional output voltage from zero to full scale. Note that fixed resistors may be connected in series and/or parallel with the variable programming resistor to set lower and/or upper output voltage limits. The resultant programming resistance is the sum of the series/parallel resistor combination, and must be between 0 and 4000 ohms. For example, a 2000 ohm resistor connected in series with the variable programming resistor will set the lower limit for output voltage at one-half full scale. 36 Operating Instructions Note: If the programming terminals (VP to P) become open circuited during resistance programming, the output voltage will rise above the power supply rating. The supply will not be damaged if this occurs, but the overvoltage trip point should be properly adjusted to protect the user’s load. = Handle Figure 3-7. Resistance Programming of Output Voltage Constant Voltage Output, Voltage Control. The setup shown in Figure 3-8 allows the output voltage to be varied by using an external voltage source to program the supply. A voltage source variable from 0 to + 5 volts produces a proportional output voltage from zero to full scale. The static load on the programming voltage source is less than 5mA. A source resistance of less than 10k is necessary to avoid degradation of offset and drift specifications. Note: If external resistors are used to limit the remote-programming voltage to 5Vdc, the resulting high programming-source resistance can degrade the power supply’s programming speed, offset and drift performance. Limit the equivalent source resistance to 10k ohm maximum. Figure 3-9 shows a convenient way to calculate suitable voltage-divider resistance values for a 5k ohm source resistance. = Handle Figure 3-8. Voltage Programming of Output Voltage Operating Instructions 37 = Handle = Handle Figure 3-9. Optional Voltage Divider for Program Source Constant Current Output, Resistance Control. The setup shown in Figure 3-10 allows the output current to be varied by using an external resistor to program the supply. A programming resistor variable from 0 to 4000 ohms produces a proportional output current from zero to full scale. Note that fixed resistors may be connected in series and/or parallel with the variable programming resistor to set lower and/or upper output current limits. The resultant programming resistance is the sum of the series/parallel resistor combination, and must be between 0 and 4000 ohms. For example, a 2000 ohm resistor connected in series with the variable programming resistor will set the lower limit for output current at one-half full scale. Caution: If the programming terminals (IP to P) become open circuited during resistance programming the output current will tend to rise above rating. The power supply will not be damaged if this occurs, but the user’s load may be damaged. If there is a possibility that the programming leads may be opened, it is suggested that the optional resistor be connected directly across terminals IP and P, as shown in Figure 3-10. The value of this resistor should be selected to limit the output current to the maximum that the load can handle without damage. For example, if the load can handle half the current rating of the power supply, a 2000 ohm resistor should be connected from IP to P. If this resistor is used, the actual resistance value programming the supply is the parallel combination of the two resistors. = Handle Figure 3-10. Resistance Programming of Output Current 38 Operating Instructions Constant Current Output, Voltage Control. The setup shown in Figure 3-11 allows the output current to be varied by using an external voltage to program the supply. A voltage source variable from 0 to + 5 volts produces a proportional output current from zero to full scale. The static load on the programming voltage source is less than 5mA. A source resistance of less than 10k is necessary to avoid de...

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