TM 11-6625-2958-14&P

Figure 3-5.Remote Voltage Programming,

Non-Unity Gain (Constant Voltage)

(less than 30ppm Per degree Centigrade) characteristics in order to maintain the Supply's temperature and stability specifications. Reference resistor RR should not exceed 10K. Note that it is possible to use the front panel voltage control already in the supply (A5R121) as the voltage gain control (Rp) by simply removing the external Rp and strapping terminals Al and A2 together.

3-31 The output voltage of the supply may be adjusted to exactly zero when the external programming voltage is zero by either inserting and adjusting R111 as discussed in Paragraph 5-84,or, if the instrument is equipped with Option 020, by adjusting potentiometer R112 as discussed in Paragraph 5-86.

3-32REMOTE PROGRAMMING, CONSTANT CURRENT

3-33 Either a resistance or a voltage source can be used to control the constant current output of the supply. The CURRENT controls on the front panel are automatically disabled in the following procedures.

3-34 Resistance Programming (Figure 3-6). In this

mode, the output current varies at a rate determined

by the programming

coefficient as

follows:

Model

Programming

Coefficient

6259B

4 ohms/ampere

6260B

2 ohms/ampere

6261B

4 ohms/ampere

6268B

6 ohms/ampere

6269B

4 ohms/ampere

The programming coefficient is determined by the constant current programming current which is adjusted to within 10% of 2.5mA at the factory. If greater programming accuracy is required, it may be achieved by either adjusting R30 as discussed in Paragraph 5-97,or, if the instrument is equipped

Figure 3-6.Remote Resistance Programming

(Constant Current)

with Option 021, by adjusting potentiometer R116 as discussed in Paragraph 5-98.The output current of the supply when zero ohms is placed across the programming terminals may be set to exactly zero by either inserting and adjusting R117 as discussed in Paragraph 5-92,or, if the instrument is equipped with Option 021, by adjusting potentiometer R119 as discussed in Paragraph 5-94.

3-35 Use stable, low noise, low temperature coefficient (less than 30ppm/°C) programming resistors to maintain the power supply temperature coefficient and stability s pacifications. A switch may be used to set discrete values of output current. A make-before-break type of switch should be used since the output current will exceed the maximum rating of the power supply if the switch contacts open during the switching interval.

C A U T I O N

If the programming terminals (A4 and A 6) should open at any time during the remote resistance programming mode, the output current will rise to a value that may damage the power supply and/or the load. If, in the particular programming configuration in use, there is a chance that the terminals might become open, it is suggested that a 200 ohm resistor be connected across the programming terminals. Like the programming resistor, this resistor should be a low noise, low temperature coefficient type. Not e that when this resistor is used, the resistance value actually programming the supply is the parallel combination of the remote programming resistance and the resistor across the programming terminals.

3-4