Compare 2700 Series and 3700 Series Switches (1)

To illustrate the potential of TSP, let's look at several SCPI application examples for the 2700 Series and compare them to the 3700 Series scripts. But first, we'll review our understanding of channel numbers. Essentially, the difference is that the 2700 Series uses 3 digits, while the 3700 Series uses 4. The extra digit represents the 100th position and is most commonly used for backplane channels.

2700 series: (@101:110)

3700 series: ("1031,1921")

It is noteworthy how both series use the comma ',' to indicate separate channels and the semicolon ':' to include all channels between them.

To specify the channel number,

Series 2700: (@101) = Series 2700: (@101)

Slot #=slot number

Channel #=Channel number

place=location

Series 3700: ("1031")=Series 3700: ("1031")

The switching capabilities of the 3700 Series instruments are more powerful than those of the 2700 Series. Designated channels are included in the digital backplane channels. Backplane channels connect the switch output to the measuring instrument (DMM). The 2700 Series backplane relays are closed by default. Disconnecting the backplane channels disconnects the internal DMM. Backplane channels can be independently controlled by disconnecting the DMM input terminals using the ROUT:MULTI instruction. In other words, backplane channels cannot be controlled using the sweep function. This limitation requires detailed management of the DMM function, opening/closing channels, and backplane relays. Refer to the 2700 Series instrument manual for details.

The 3700 Series backplane relays are disconnected by default. In addition to the DMM connection backplane channels, there are 4 analog backplanes for interconnection between cards. Direct access to the analog backplane allows for flexible configuration of switches that is not possible with the 2700 Series. Also, the 3700 Series is more powerful in terms of controlling the opening and closing as well as the relay connection methods. As expected, this flexibility leads to a variety of options for applying ICL instructions, which will be discussed in the next section.

Closed channel

2700 Series:

The ROUT:CLOS instruction is used to close the specified channel. However, this instruction can also disconnect all channels before closing the specified channel. If you need to keep a channel closed while closing another channel, use the ROUT:MULTI instruction.

The SCPI command ROUT:CLOSE(@101) executes the following sequence:

1. Break-before-make connection

2. Open all previously closed channels

3. Close the channel 1 of the slot 1, including the corresponding back plate

3700 Series:

The 2700 Series offers two channel close instructions (:ROUT:CLOS and :ROUT:MULT:CLOS); the 3700 Series has four unique channel close instructions. Each instruction performs channel close in a slightly different way, which increases flexibility and provides various advantages in instruction selection. For example, a "switch only" instruction does nothing else but configures the DMM, or ensures that the measurement channel is intact to provide measurement integrity. Then, other instructions not only close the channel, but also perform additional tasks to configure the DMM function and ensure that the switch is closed correctly in this configuration. Here is a list of the instructions and what each instruction does:

dmm.close: automatically closes the corresponding backplane channel that is associated with a function. By default, channels have no associated functions. This command will report an error when a channel has no associated measurement function. The command that associates channels and functions is the dmm.setconfig command. For example, dmm.setconfig("1031","dcvolts") associates the DC voltage function to channel 31.

dmm.close performs 4 sequential tasks:

1. Disconnect the channels related to the card row

2. Disconnect all backplane relays of other cards connected to analog backplanes 1 and 2

3. Close the specified channel and the corresponding backplane relay to connect the closed channel to the DMM

4. Configure the DMM as specified previously

channel.close: Similar to the 2700 Series :ROUT:MULT:CLOS command, this command will never change the DMM function, open a channel, or close the corresponding backplane channel (unless the backplane relay is part of the channel list or configured via the channel.set.backplane command). In fact, this low-level command strictly closes the selected channel. This command implements the most switch and timing control because it does not perform any background or switch management tasks.

channel.exclusiveclose: Similar to the ROUT:CLOS command of the Series 2700 instruments, which closes the specified channel (and disconnects all other channels), this exclusive close command disconnects the previously closed channels and analog backplane relays on all slots, and then closes the requested channel and the specified analog backplane relay.

Channel.exclusiveslotclose: Before closing the specified channel, only previously closed channels on all slots associated with the channel in the channel list are disconnected.