3
3. Operating Considerations and Precautions
1.
While operating in the voltage mode, the calibrator’s output circuitry can
sink or source up to 1mA max. Loads greater than 1mA may cause the
calibrator to drop out of its accuracy specification. (See Figure 1)
When there is an excessive load, the word “OVERLOAD” will appear
intermittently on the LCD readout. Long term short circuit conditions will
not harm the calibrator but will cause the battery to decay. Maximum
short circuit is 25 mA.
Figure 1
PCL422A operating as a Precision Voltage Source
2.
In the current mode, the maximum load driving capacity of the PCL422A
is 1000 ohms. If connections to the mA jacks are open or the load is
greater than the compliance voltage while trying to source a current, the
word “OPEN LOOP” will appear intermittently on the LCD readout. (See
Figure 2)
Figure 2
PCL422A operating as a Current Source
3.
Current loop devices that derive their power supply from an external
power supply can be calibrated as shown in Figure 3.
Figure 3
PCL422A indicating current using an external power supply
+
−
+
−
mA
Volts
Unit
Under
Test
Max. Load
1 mA
(+)
(–)
+
−
+
−
mA
Volts
Unit
Under
Test
(+)
(–)
O to 24mA
up to
1000 ohms
+
−
+
−
mA
Volts
Unit
Under
Test
Power
Supply
(+)
(+)
4 to 20mA
30 Volts
Max.