Ranges
NI power supplies and SMUs use one or more ranges for voltage and current output, as well as one or more ranges for voltage and current measurement. Use the highest resolution (smallest) range possible for a particular application to get maximum output and measurement accuracy. Refer to the specifications document for your device or NI PXI-4110 or NI PXI-4130 for more information about what ranges are available for a particular channel on your device.
Ranges are typically described as the maximum possible value from zero that the range can output or measure (not including the overrange). For example, in the 20 mA current level range, the current level can be configured up to 20 mA.
When configuring an output range, if you request a range that differs from the ranges described in your device specifications, NI-DCPower selects the highest resolution (smallest) range available that accommodates the requested range. For example, on a device with only 20 mA and 200 mA current limit ranges, if you request 100 mA for the current range, NI-DCPower selects the 200 mA range.
There are four configurable output ranges for each device channel : voltage level range, current limit range, current level range, voltage limit range. When the output function is set to NIDCPOWER_VAL_DC_VOLTAGE using the niDCPower_ConfigureOutputFunction function or DC Voltage using the niDCPower Configure Output Function VI, the voltage level range and current limit range are in use. When the output function is set to NIDCPOWER_VAL_DC_CURRENT using the niDCPower_ConfigureOutputFunction function or DC Current using the niDCPower Configure Output Function VI, the current level range and voltage limit range are in use.
Changing Ranges
You can use the following four VIs and functions to configure output ranges for your device.
The configured range must be able to accommodate the configured output value. For example, if the current limit range is 1 A and the current limit is 50 mA, changing the current limit range to 20 mA is not allowed because 50 mA is not possible in the new range. When changing ranges in immediate configuration mode be aware of the order of the output range and output value changes because the configuration change takes effect immediately in this mode. To avoid ordering issues, NI recommends that you configure the output range and output value in delayed configuration mode. In this mode you can configure the output range and the output value in any order. Alternatively, you can enable autoranging for the range you want to change.
Overranging
If the niDCPower Overranging Enabled property or the NIDCPOWER_ATTR_OVERRANGING_ENABLED attribute is set to TRUE, the valid values for the programmed output (voltage level, current limit, current level, and voltage limit) may be extended beyond their normal operating range on channels that support this feature. Enabling overranging for a particular device enables this feature for both output current and voltage on all channels. Refer to NI PXI-4110 or NI PXI-4130 to determine if your device supports overranging.
Output Autoranging
When autoranging is enabled for an output range, NI-DCPower automatically changes the output range based on the configuration output value. NI-DCPower automatically changes to the highest resolution (smallest) range that can accommodate the configured output value. You can selectively enable autoranging for any output range on a channel.
Use the following properties and attributes to configure your device for autoranging.