VXi VT1422A Manual De Usuario

To link channels to the resistance EU conversion send the 
[SENSe:]FUNCtion:RESistance  
<excite_current>,[<range>,](@<ch_list>) command.

Resistance measurements assume that there is at least one Current Source 
SCP installed (eight current sources per SCP). See Figure 4-5.

•

The <excite_current> parameter is used only to tell the EU conversion 

what the Current Source SCP channel is now set to. <excite_current> 
is specified in amps dc and the choices for the VT1505A SCP are 
30e-6 (or MIN) and 488e-6 (or MAX). Select 488 µA for measuring 
resistances of less than 8,000 

Ω. Select 30 µA for resistances of 

8,000

Ω and above.

•

The optional <range> parameter can be used to choose a fixed A/D 

range. When not specified (defaulted), the module uses auto-range.

•

The <ch_list> parameter specifies which channel(s) to link to the 

resistance EU conversion. These channels will sense the voltage across 
the unknown resistance. Each can be a Current Source SCP channel 
(a two-wire resistance measurement) or a sense channel separate from 
the Current Source SCP channel (a four-wire resistance measurement). 
See Figure 4-5 for diagrams of these measurement connections.

* Because of the 150 ohm resistor in series with each of the

current source outputs, Two-Wire resistance and temperature
measurements will have a 300 ohm offset.

** The current source Hi terminal is the negative voltage node.

The current source LO terminal is the positive voltage node.

Two-Wire Measurement

(not recommended **)

Current Source SCP

Field Wiring

Sens

e

C

h

annel

*150 ohm 5%

*150 ohm 5%

R

Four-Wire Measurement

Current Source SCP

Field Wiring

HI

LO

HI

LO

R

Any Sense SCP

Sens

e

C

h

annel

HI

LO