Considerations when Migrating to the NI 4065 from Existing NI 4060 Applications

The NI 4065 takes advantage of National Instruments latest technology to provide a high performance alternative to the NI 4060. This whitepaper describes differences between the devices and considerations that should be made when migrating to a NI 4065 based system from one that used the NI 4060.

Instrument Descriptor Naming Convention

The NI 4065 is based on the NI-DAQmx driver which uses a different instrument descriptor naming convention than the NI 4060. A feature can be used to avoid modifying code that uses the traditional naming convention (DAQ::1::INSTR) to refer to a newly installed NI 4065 device. To do this, launch Measurement and Automation Explorer, expand NI-DAQmx devices under Devices and Interfaces, right-click the device of interest, and select rename. Then rename the device using only the number of the previous Traditional NI-DAQ (Legacy) resource. For example: If an existing NI 4060 application used an instrument descriptor such as DAQ::2::INSTR, then the new name given to the NI 4065 listed as a DAQmx device should just be 2.

NOTE: If the user has access to modify the code, the instrument descriptor can always be changed to match the instrument descriptor in MAX.

Switching Applications

When using the NI 4060 to control SCXI switches, please consider that the NI 4065 cannot control SCXI chassis configured as Traditional NI-DAQ (Legacy) devices. Applications that incorporate the use of SCXI switch modules could be impacted by replacing the NI 4060 with the NI 4065 if they rely on the DMM for SCXI control via the auxiliary front panel connector or chassis backplane of a PXI/SCXI combination chassis.

Below are a few scenarios a user may encounter when migrating from a SCXI switching application that uses the NI 4060.

Applications that use NI-Switch to program a switch device

For existing applications that rely on a Traditional NI-DAQ (Legacy) SCXI chassis configuration in MAX, there are two options:

1. To continue using the DMM as the chassis controller, a new NI-DAQmx based SCXI chassis must be created in MAX. Please refer to the SCXI Configuration Wizard for examples. The new instrument descriptor should be used by NI-Switch to reference the new configuration.
2. An alternate Traditional NI-DAQ (Legacy) device can be used to control the chassis such as any E-Series DAQ device. The chassis configuration will have to be modified to point to this device as the new chassis communicator.

Applications that use NI-DAQmx to program a switch device

No configuration changes are necessary.

Additional Consideration

The NI 4060 configured as an SCXI controller automatically sets the Measurement Complete (MC) destination to the location where SCXI is configured (external or internal PXI/SCXI trigger lines). The NI 4065 configured as an SCXI controller automatically sets the MC destination to NONE. If your application relies on the routing behavior of the NI 4060 by not explicitly calling niDMM Configure Measurement Complete Destination, you must modify your application by calling this VI/function.

Alternately, the NI 4065 can emulate NI 4060 routing behavior by specifying a registry key. Please see the NI-DMM readme for more information.

Auto Zero

The NI 4065 hardware architecture implements a measurement technique that integrates offset compensation for each measurement without sacrificing reading rate. For this reason, Auto Zero is always enabled when using the NI 4065. In all default configurations, the NI-DMM driver handles the state of Auto Zero automatically. If you’ve chosen to use advanced configuration features to explicitly set the Auto Zero feature of your NI 4060 device, your application when used with a NI 4065 may generate an error. If Auto Zero is explicitly set to ONCE or OFF, an error will be returned stating the user has specified an invalid value for the parameter or property.

A straightforward solution to the problem is to set this function, property or attribute to one of the other two supported values: ON or AUTO. AUTO will allow the driver to select the best value in order to achieve the resolution specified in other configuration functions. Since Auto Zero is always enabled for the NI 4065, ON and AUTO are equivalent. Most existing applications will already have Auto Zero enabled. In all others, enabling Auto Zero will have little impact on the application itself and improves measurement quality without sacrificing speed.

Measurement Range Coercion

NI 4065 measurement ranges differ from the NI 4060. Use the table below to find coerced values used by NI-DMM when you specify NI 4060 supported ranges. If these values are not optimal for the signal you’re measuring, consider modifying the range settings in the NI-DMM code.   For example, if the range was set to 25 V for the 4060, it would be coerced to 100 V for the 4065.  If this new range is not optimal, change the code to another range such as 10 V.  For more information regarding the resolution and accuracy for the supported ranges, please see the NI 4065 Specifications.

Reading Rate

A NI 4060 application may rely on the time it takes the device to take measurements while performing another task in parallel. It is possible the increased performance of the NI 4065 could introduce undesired application behavior. For example, if both boards are configured for 5 ½ digit measurements the NI 4065 can measure at rates as fast as 1500 S/s (samples per second), whereas the NI 4060 is only capable of measuring at rates of 60 S/s.

If an existing application explicitly sets the measurement period in units of PLCs (Power Line Cycles) the NI 4065 can use these aperture settings to effectively reproduce the same aperture time. The NI 4065 is capable of achieving aperture times at discrete periods including 333 us, 667 us, 1.11 ms and integer multiples of 1.11 ms up to 78.2 seconds. When using the NI 4065, differences in the overall measurement period may occur due to changes in the other measurement phases, such as switch and settle time.

Physical Characteristics

There are two distinct differences between the NI 4060 and the NI 4065 front panel connectors.  These differences pertain to current measurements and PCI keying.   

Current Measurements

The front panel connectors used to measure current differ from the NI 4060 to the NI 4065. In applications that require current measurement, cables must be rearranged according to Figure 1. This must be taken into account for applications that use custom front panel terminal blocks.

PCI Keying

The PCI connector of the PCI-4065 is keyed for both 5 V and 3.3 V supply voltages. The NI 4065 requires both of these supplies to operate correctly. Some older PCs may only provide a 5 V supply, which is the only supply necessary for the NI 4060. Please consult your owner’s manual for the motherboard you are using to ensure that it supports both 3.3 V and 5 V supply lines. For more information regarding known compatibility issues with motherboards that do not provide 3.3 V supply lines, please see Knowledgebase 3DKF8P33.

Downloads

dmmfrontconnector.png

1 ratings | 5.00 out of 5

Print

Reader Comments | Submit a comment »