Tektronix DMM4020 Digital-Multimeter, DMM, VFD-Multiple segment, 20000 counts CAT II 600 V DMM4020-A1 Data Sheet

3-16 

The Meter features a trigger function that allows you to select a measurement trigger 

source. When the trigger mode is set to 3 or 5, the delay between receiving the trigger 

and the start of a measurement is 400 ms. Refer to Chapter 1 for trigger delay response 

specifications. Upon completion of each measurement, a “measurement-complete” signal 

(low-true pulse) is sent to the external trigger terminal on the rear panel. See the 

“Electrical Specifications” section in Chapter 1 for information on this signal.  
The following sections discuss triggering the Meter automatically using its internal 

trigger, or externally using the trigger key on the front panel and the trigger terminal on 

the rear panel. 

There are five possible sources for triggering a measurement:  

•

  Mode 1 is automatic. Measurements are triggered internally and are continuous 

and occur as fast as the configuration will allow. 

•

  Mode 2 is triggered without delay using J. 

•

  Mode 3 is triggered with delay using J. 

•

  Mode 4 is triggered without delay by an external signal. 

•

  Mode 5 is triggered with delay by an external signal.  

To select a trigger source: 

1.  Press Q then J. 
2.  Press U or V to choose the trigger mode. 
3.  Press R and hold for 2 seconds to save the selected mode. 

The Meter provides two external trigger connection methods for different operation 

modes. Table 3-4 shows the layout of the TRIG/IO_RS232 connector.  
An external TTL signal on pin 9 will trigger a measurement cycle. Alternatively, pin 9 of 

the RS-232 interface can be connected to pin 1 through an external switch. See Figure 3-

12. A measurement cycle is trigger when the switch is closed and the +5 volts from pin 1 

is applied to pin 9. The trigger event occurs on the rising edge of the signal applied to 

pin 9.