National Instruments 6110 Manual

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February 2003
370050B-01
NI 6110/6111/6115/6120
CALIBRATION PROCEDURE
This document describes the procedure for verifying and adjusting a
National Instruments 6110/6111/6115/6120 data acquisition (DAQ)
device. This document contains four main sections:
•Introduction—This section tells you what calibration is, whyyou
should calibrate devices, and how often you should calibrate.
•Equipment and Other Test Requirements—This section describes
what you must do before calibrating the device, including an overview
of the test equipment, software, calibration functions, and environment
needed for calibration.
•Calibration Process—This section provides step-by-step instructions
for verifying and calibrating your device.
•NI 6110/6111/6115/6120 Specifications—This section provides
specification tables for the NI 6110/6111/6115/6120.
This document is intended for metrology labs. It does not cover
programming technique or compiler configuration because of the number
of programming languages and styles you can use to calibrate the device.
However, NI-DAQ has many online help files that contain
compiler-specific instructions and function explanations. You can install
these help files when you install NI-DAQ.
Introduction
What Is Calibration?
Calibration is a set of operations that compares the values indicated by a
measuring instrument or measuring system to the corresponding values
realized by external standards. The result of a calibration can be used to
determine the measurement error and can correct for it in the adjustment
process.
The calibration process consists of verifying, adjusting, and reverifying a
device. During verification, you compare the measured performance to an
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NI 6110/6111/6115/6120 Calibration Procedure 2 ni.com
external standard of known accuracy to confirm that the product meets or
exceeds specifications. During adjustment, you correct the measurement
error of the device by adjusting the calibration constants and storing the
new calibration constants in the EEPROM. The host computer reads the
calibration constants, and the software uses them to compensate for errors
in the data and to present calibrated data to the user.
Why Should You Calibrate?
The accuracy of electronic components drifts with time and temperature,
which can affect measurement accuracy. Calibration restores these
components to the specified accuracy and ensures that the device still meets
NI standards.
How Often Should You Calibrate?
The measurement requirements of your measurement application
determine how often you should calibrate the device. NI recommends
performing a complete calibration at least once every year. You can shorten
this interval based on the demands of your application.
Equipment and Other Test Requirements
This section describes the equipment, software, documentation, and test
conditions needed for calibration.
Equipment
When calibrating an NI 6110/6111/6115/6120, NI recommends that you
use the following instruments:
• Calibrator—Fluke 5700A
• Digital Multimeter (DMM)—NI 4070
• Counter—Agilent (HP) 53131A
If these exact instruments are not available, use the following accuracy
requirements to select substitute calibration standards:
• A high-precision voltage source that is at least 50 ppm accurate
• A multiranging 5 1/2-digit DMM accurate to within 15 ppm
• A counter accurate to 0.01%
Note If you do not have custom connection hardware available, you may need a connector
block, such as the NI TBX-68, and a shielded 68-pin connector cable. These components
give easy access to the individual pins on the 68-pin I/O connector.

©National Instruments Corporation 3 NI 6110/6111/6115/6120 Calibration Procedure
Documentation and Software
The following documentation and software are required to calibrate the
NI 6110/6111/6115/6120:
• The latest version of NI-DAQ. You can download this from ni.com
by clicking Download Software.
•niECal.dll, niECal.lib, and niECal.h files, available from
ni.com/calibration by clicking Manual Calibration
Procedures.
•NI-DAQ User Manual for PC Compatibles, available from
ni.com/manuals.
You also need the NI-DAQ Function Reference Help, which is installed
with NI-DAQ. To access this file, go to Start»Programs»National
Instruments»NI-DAQ»NI-DAQ Help.
Documentation
The NI-DAQ Function Reference Help and the NI-DAQ User Manual for
PC Compatibles contain information on using NI-DAQ. The function
reference file includes detailed information on the functions in the driver.
The user manual provides instructions on installing and configuring
National Instruments DAQ devices and describes how to create
applications that use NI-DAQ. These documents are your primary
references for writing a calibration utility. For more information on the
products you are calibrating, refer to the device user manuals.
Software
NI-DAQ supports a number of programming languages, including
LabVIEW, Measurement Studio, Microsoft Visual C++, Microsoft Visual
Basic, and Borland C++. When you install NI-DAQ, install support for the
programming language you are using.
The niECal.dll, niECal.lib, and niECal.h files provide calibration
functions that are not provided by NI-DAQ. These functions include
protecting the calibration constants and updating the calibration date.
You can access the functions in this .dll through any 32-bit compiler.
Writing Your Calibration Procedure
The calibration process is described in the Calibration Process section. The
description includes step-by-step instructions on calling the appropriate
calibration functions. Unless otherwise specified, the calibration functions
are C function calls in NI-DAQ. These function calls are also valid for
Visual Basic programs. While LabVIEW virtual instruments (VIs) are not
discussed, the translation from NI-DAQ function calls to LabVIEW VIs is

NI 6110/6111/6115/6120 Calibration Procedure 4 ni.com
straightforward, as many of the VIs have the same names as the listed
function calls. Refer to the Creating Verification and Calibration Code
section for flowcharts detailing the code used at each step of the calibration
procedure.
You must follow a number of compiler-specific steps to create an
application using NI-DAQ. The NI-DAQ User Manual for PC Compatibles
details the required steps for each of the supported compilers.
Many of the functions listed in the calibration procedure use variables that
are defined in the nidaqcns.h file. To use these variables, you must
include the nidaqcns.h file in your code. If you do not wish to use these
variable definitions, you can examine the function call listings in NI-DAQ
documentation and the nidaqcns.h file to determine what input values
are required.
Test Conditions
To optimize connections and test conditions during calibration, use the
following guidelines:
• Keep connections to the device as short as possible. Long cables and
wires can act as antennae, picking up extra noise that can affect
calibration.
• Use shielded copper wire for all cable connections to the device.
Use twisted-pair wire to eliminate noise and thermal offsets.
• Maintain a temperature between 18 and 28 °C. To operate the device
at a specific temperature outside this range, calibrate the module at that
temperature.
• Keep relative humidity below 80%.
• Allow a warm-up time of at least 15 minutes for PXI/PCI/AT bus
devices and 30 minutes for PCMCIA devices to ensure that the
measurement circuitry is at a stable operating temperature.
Calibration Process
The calibration process consists of four main steps.
1. Creating Verification and Calibration Code
2. Verifying the Performance of the NI 6110/6111/6115/6120—This step
determines whether the device is in specification prior to calibration.
3. Adjusting the Device—This step adjusts the calibration constants with
respect to a known voltage source.

©National Instruments Corporation 5 NI 6110/6111/6115/6120 Calibration Procedure
4. Reverifying the Device—This step verifies the performance of the
device after adjusting, to ensure the device operates within
specifications after calibration.
These steps are described in the following sections.
Creating Verification and Calibration Code
This section shows the basic flowcharts for creating the verification and
adjustment code for the NI 6110/6111/6115/6120 calibration procedure.
These flowcharts only refer to the appropriate NI-DAQ function calls.
You may want to refer to the Calibration Process section, to the NI-DAQ
Function Reference Help, and to the NI-DAQ User Manual for PC
Compatibles for additional information on the software structure and for
function explanations.
Verifying Analog Input
Figure 1. Analog Input Verification
From the specification table for the product,
determine the gain, input range, and polarity to verify.
AI_Configure(deviceNumber,chan,0,inputRange,polarity,0)
DAQ_Op(deviceNumber,chan,gain,buffer,1000,10000)
DAQ_VScale(deviceNumber,chan,gain,1,0,1000,buffer,voltArray)
The final measurement is the average of the 1,000 samples.

NI 6110/6111/6115/6120 Calibration Procedure 6 ni.com
Verifying Analog Output
Figure 2. Analog Output Verification
Verifying the Counter
Figure 3. Counter Verification
AO_Configure(deviceNumber,chan,outputPolarity,0,10,0)
From the specification table for the product,
determine the channel, output polarity, and voltage to verify.
AO_VWrite(deviceNumber,chan,voltage)
GPCTR_Control(deviceNumber,chan,ND_RESET)
GPCTR_Set_Application(deviceNumber,chan,ND_PULSE_TRAIN_GNR)
GPCTR_Change_Parameter(deviceNumber,chan,ND_COUNT_1,2)
GPCTR_Control(deviceNumber,chan,ND_PROGRAM)
GPCTR_Change_Parameter(deviceNumber,chan,ND_COUNT_2,2)
Select_Signal(deviceNumber,ND_GPCTR0_OUTPUT,ND_GPCTR0_OUTPUT,ND_LOW_TO_HIGH)

©National Instruments Corporation 7 NI 6110/6111/6115/6120 Calibration Procedure
Adjusting the Device
Figure 4. Device Adjustment
Configuring the Device for Calibration
Measurement & Automation Explorer (MAX) ships with NI-DAQ and
automatically detects the NI 6110/6111/6115/6120. However, for NI-DAQ
to communicate with the device, you must configure the device in MAX.
For information on configuring an NI 6110/6111 refer to Chapter 2,
Installing and Configuring the NI PCI-6110/6111,of the
NI PCI-6110E/6111E User Manual. For information on configuring an
NI 6115/6120, refer to Chapter 2, Installing and Configuring the
NI 6115/6120, of the NI 6115/6120 User Manual.
The following procedure describes how to configure a device with
NI-DAQ.
1. Install NI-DAQ. The latest version is available at ni.com.
2. Power off the computer and install the device in an available slot.
3. Power on the computer and launch MAX.
4. Configure the device number and click Test Resources to ensure the
device is working properly.
You have completed configuring the device for calibration.
Note When MAX configures a device, it assigns a device number. Each function call uses
this number to identify which DAQ device to calibrate. Make note of this number so that
you have it when you make function calls.
Calibrate_E_Series(deviceNumber,ND_SELF_CALIBRATE,ND_USER_EEPROM_AREA,0)
Get_Cal_Date(deviceNumber,*CalDate)
Calibrate_E_Series(deviceNumber,ND_EXTERNAL_CALIBRATE,ND_USER_AREA,7.5)
Copy_Cal(deviceNumber)
Calibrate_E_Series(deviceNumber,ND_SET_DEFAULT_LOAD_AREA,ND_FACTORY_EEPROM_AREA,0)

NI 6110/6111/6115/6120 Calibration Procedure 8 ni.com
Verifying the Performance of the NI 6110/6111/6115/6120
This section describes the verification procedures for calibrating the
NI 6110/6111/6115/6120. You must verify analog input, analog output,
and the counter performance.
Verifying Analog Input
To verify the performance of the analog input of the device, complete the
following steps:
1. Read the Equipment and Other Test Requirements section.
Note Calibrator connections depend on the channel you are verifying. The verification
process requires you to individually test each channel.
2. Use the following guide to determine the connections between the
calibrator and the device pins for analog input verification.
a. Starting with channel 0, connect the positive output of the
calibrator to the analog input specified in Table 1.
b. Connect the negative output of the calibrator to the analog input
specified in Table 2.
Table 1. Positive Output Connections
Device Channel Analog Input
068
133
265
330
Table 2. Negative Output Connections
Device Channel Analog Input
034
166
231
363

©National Instruments Corporation 9 NI 6110/6111/6115/6120 Calibration Procedure
3. If the calibrator and computer are floating with respect to each other,
connect the negative output of the calibrator to the analog input
channel ground, as listed in Table 3.
4. Refer to the NI 6110/6111/6115/6120 Specifications section for all
acceptable settings for the device. Although NI recommends that you
verify all ranges, you can save time by checking only the ranges your
application uses.
5. Set the calibrator voltage to the test point value indicated in Table 5 for
the NI 6110/6111, Table 8 for the NI 6115, or Table 11 for the
NI 6120.
6. Call AI_Configure to inform NI-DAQ of the input mode, input
range, and input polarity selected for the device. Set the following
parameters:
•deviceNumber—The value obtained from MAX
•chan—The channel currently being verified
•inputMode—0
•inputRange—The range for calibration from Table 5 for the
NI 6110/6111, Table 8 for the NI 6115, or Table 11 for the
NI 6120
•polarity—0
•driveAIS—0
7. Call DAQ_Op to acquire 1,000 points of voltage data. Set the following
parameters:
•deviceNumber—The value obtained from MAX
•chan—The channel currently being verified
•gain—The value specified by Table 5 for the NI 6110/6111,
Table 8 for the NI 6115, or Table 11 for the NI 6120
•buffer—Array of conversion samples returned
•count—1,000
•sampleRate—20,000
Table 3. Channel Ground Connections
Channel Ground Analog Input
ACH0GND 67
ACH1GND 32
ACH2GND 64
ACH3GND 29

NI 6110/6111/6115/6120 Calibration Procedure 10 ni.com
8. Call DAQ_VScale to convert the buffer of acquired binary values into
voltage values. Set the following parameters:
•deviceNumber—The value obtained from MAX
•chan—The channel currently being verified
•gain—The value specified by the appropriate analog input value
table
•gainAdjust—1
•offset—0
•count—1,000
•binArray—Binary data returned from DAQ-OP
•voltArray—Double precision array of voltage values
9. Average the 1,000 voltage values. Compare the resulting average to
the upper and lower limits listed in the appropriate table. If the result
is between these values, the device has passed this test.
10. Repeat steps 4–9 to verify all values.
11. Make the appropriate connections to verify the next channel by
repeating steps 2 and 3, and proceed from step 4.
You have completed verifying the analog input levels on the device.
Verifying Analog Output
This procedure verifies the performance of the analog output. Check
measurements using the following procedure:
1. Read the Equipment and Other Test Requirements section.
Note The NI 6110/6111/6115/6120 has two analog outputs: DAC0OUT and DAC1OUT.
This test verifies the performance of both analog output channels.
2. Connect the DMM to DAC0OUT as shown in Table 4.
3. Refer to the analog output value tables in the NI 6110/6111/6115/6120
Specifications section. These tables show acceptable settings for the
device.
Table 4. Connections to Analog Outputs
Analog Output DMM Positive Input DMM Negative Input
DAC0OUT DAC0OUT (pin 22) AOGND (pin 54)
DAC1OUT DAC1OUT (pin 21) AOGND (pin 55)