1Voltage Input Range
An A/D converter measures an applied voltage within a specific voltage input range, and each channel's voltage range
is independently software programmable. A 16bit A/D converter, for example, resolves the range to one part in 65K.
For example, a voltage applied with a ±5V range is resolved to one part in 65536 (i.e. {+5V - -5V} / 65536 = 312uV).
The input voltage range is set with the "Range" popup menu within the
Hardware settings area.
2Analog Channel Filter
Voltage measurement products sometimes include independent software programmable analog low pass filters on each channel
(e.g. i423, i100). These attenuate
frequencies above the "cutoff frequency", which is specified in the the "Low Pass" popup menu in the
Hardware settings area.
For details on a specific product, please refer to its voltage input specifications.
See Also: Noise Reduction Techniques.
3Signal Averaging Per Point ("integration")
A/D Averaging, also known as "Integration", is independently programmable for each channel, and reduces noise
by averaging many A/D samples. Averaging is done by instruNet software and is transparent to the end user.
One sets integration to 0.0 to 0.1 seconds, in 0.000006 second increments, in the
Hardware Settings area (Seconds units).
Noise is reduced by the square root of the number of a/d samples that are averaged. For example, if 100 samples
are averaged, noise is reduced 10 fold (e.g. 10mVrms to 1mVrms). Averaging also limits the maximum sample rate.
For example, if one averages each point in one channel for 1mSec, then the maximum sample rate would be 1000s/sec.
See Also: Sample Rate Vs. Integration Vs. Noise.
4Channel Switching Settling Time
When the A/D converter switches from one channel to another channel, one must wait for internal amplifier electronics
to settle to the new voltage. The "Channel Switch Settling Time" duration is automatically managed by
instruNet software and is often less than 10uSec.
5Channel Amplifier Bandwidth
The signal applied to the voltage input pin passes through an internal amplifier before reaching the internal A/D converter.
The amplifier is capable of passing frequencies up to the "Channel Amplifier Bandwidth" frequency;
at which point, higher frequencies are attenuated.
6System Noise
The System Noise is a random signal that is generated within the instruNet electronics and then internally added to
the end user signal. It is often seen as a small random error added to the end user voltage.
To see this noise, attach Vin+ and Vin- to instruNet GND, digitize,
and view the resulting signal. In theory, it should be 0 Volts. In practice, one will
see a small random voltage. Noise is often described in Volts-Peak-To-Peak (Vpp) or
Volts-Root-Mean-Square (vRms) units and is mostly a function of the "Range" and "Integration" fields in the
Hardware settings area.
For example, the i430 provides 0.20 uVrms noise on the ±10mV range with 0.001 seconds of A/D Averaging.
See Also:
Sample Rate Vs. Integration Vs. Noise,
Noise Reduction Techniques
7Temperature drift between Factory-Calibration and Software-Calibration
"Additional Error Per °C If Operate Hardware at ≥ 33°C or ≤ 13°C" refers to the additional error
that one incurs from each degree C that one operates above 33°C or below 13°C. This assumes the temperature
has not changed since the last software calibration. If the ambient temperate
around the instruNet hardware is 23°C ± 10°C, then one can ignore this error; however, if the ambient
temperature is below 13°C or above 33°C, then it applies. For example, if the base absolute accuracy specification is
±(.1% + 1mV), the additional -13°C to 33°C temperature drift specification is ±(.01% + .1mV)/°C,
the ambient temperature around the instruNet hardware is 38°C (5 degrees above 33°C),
and the instruNet was software calibrated at this 38°C temperature; then the
expected accuracy is ±(.1% + 1mV) + { (38C - 33C) * ±(.01% + .1mV)/°C} = ±(.15% + .15mV)/°C. See Also:
Calibration Options,
Stability and Drift
8Temperature drift between Software-Calibration and Later-Use
"Additional Error per °C if not AutoCal after 1°C Hardware Change Since last AutoCal" refers to the additional error
that one incurs from each degree C that the ambient temperature around the instruNet
hardware has changed, in addition to a 1°C allowable difference, since the last software calibration.
For example, if the base absolute accuracy specification is
±(.1% + 1mV), the additional error since software calibration ±(.01% + .1mV)/°C,
the ambient temperature around the instruNet hardware at last calibration was 26°C,
and the current ambient temperature is 29°C (3°C change); then the
expected accuracy is ±(.1% + 1mV) + {(29 - 26 - 1°C allowance) * ±(.01% + .1mV)/°C} = ±(.12% + .12mV)/°C.
See Also:
Calibration Options,
Stability and Drift
9Time Stability Error between Factory-Calibration and Later-Use
"Additional Error Per Year if Not Factory Calibrate Hardware After 1Yr" refers to the additional error that one incurs
for each year after factory calibration, in addition to the 1st year, that one operates the instruNet hardware.
For example, if the base absolute accuracy specification is
±(.1% + 1mV), the additional error per year after 1st year is ±(.01% + .1mV)/yr,
the instruNet hardware was factory calibrated Jan 2008, and the current date is Jan 2011 (3yrs later); then the
expected accuracy is ±(.1% + 1mV) + {(3 yrs - 1 yr allowance) * ±(.01% + .1mV)/yr }= ±(.12% + .12mV)/°C.
See Also:
Calibration Options,
Stability and Drift
10Engineering Units (EU) Per Least Significant Bit (LSB) Resolution
Engineering Units (EU) refers to the units commonly used with each sensor type (e.g. °C with thermocouples)21. An A/D converter measures an applied voltage within a specific voltage input range, and each channel's voltage range
is independently software programmable. A 16bit A/D converter, for example, resolves the range to one part in 65K. The voltage that corresponds to this one part is referred to as the "Least Significant Bit" (LSB), and the Engineering Units (EU) quantity that corresponds to this one part is referred to as the EU LSB Resolution.
For example, a voltage applied to the ±80mV range is resolved to one part in 65536 with an LSB voltage resolution of 2.4uV (i.e. {+80mV - -80mV} / 65536 = 2.4uV).
In each sensor setup, one incurs a certain amount of Volts per EU,
at each EU position (e.g. J thermocouple provides 55uV/°C at 150°C and 41uV/°C at -100°C). EU LSB is specified at the largest value within the measurement range.
With a -100°C to +150°C J thermocouple on the ±80mV range, the EU LSB resolution would be 2.4uV lsb / 55uV/C = .04°C per LSB.
11Engineering Units (EU) Measurement Range
Each sensor type (e.g. voltage, current, resistance, thermocouple) is set up to measure a stimulus over a
specific engineering units (EU)21 range. For example, a thermocouple might be
set up to measure temperatures between -100°C and 200°C. Subsequently, in this case, if one applied 300°C, the system would return a
temperature of approximately 210°C ± 10°C due to hitting the top of the input amplifier voltage range ("clipping").
12mVolts Measured at Min/Max Engineering Units
Each sensor ultimately has its Engineering Units (EU)21 value converted to a
voltage that is measured by the instruNet system. "mV at min/max EU" refers to the measured voltage
at the minimum and maximum EU range. For example, if measuring a J thermocouple on the -100°C to 150°C range, -4.6mV
would be measured at -100°C, and +8mV would be measured at 150°C.
13Sensor Type
Sensor type refers to the kind of sensor attached to the measurement system. For example, thermocouples are
specified with a letter that refers to the materials in use (e.g. J, K, T); thermistors are specified as
a resistance across the device at 25°C (e.g. 2252 Ω @ 25°C); and RTD's are specified as a resistance across the device at 0°C
(e.g. 100 Ω @ 25°C).
14μVolts Measured Per Engineering Unit, at Min/Max Engineering Units
Each sensor ultimately has its Engineering Units (EU)21 value converted to a
voltage that is measured by the instruNet system. "μVolts per EU" refers to the voltage
change for each unit change of EU, at the minimum and maximum EU. For example, if measuring
a J thermocouple on the -100°C to 150°C range, one would see 41.2μV change per 1°C change
at -100°C, and 55.2μV change per 1°C change at 15°C.
15Shunt Resistor Initial Resistance (ohms)
Each resistor is manufactured with a specific resistance across the device, which is sometimes referred to as
its "initial resistance". The reason we say "initial" is because from there, it can change slightly with ambient
temperature, humidity, and age (i.e. number of years after manufacture). For example shunt resistor products, click here.
16Shunt Resistor Initial Accuracy (%) and Temperature Drift (ppm/°C)
Each resistor is manufactured with a specified maximum resistance error. For example, a 1KΩ resistor
specified as being accurate to 1% would provide an actual resistance between 0.99KΩ and 1.01KΩ. Resistor temperature drift refers
to the maximum amount of resistance change for each 1°C change of the resistor device temperature. For example, if
a 1KΩ resistor has a 10ppm/°C temperature drift specification (parts per million per degree C), and the
device is 1KΩ at 25°C, then its resistance at 50°C would be 1000Ω ± (1000Ω * 0.000010 * (50°C-25°C))
= 1000Ω ± 0.25Ω. For example shunt resistor products, click here.
17Sample Rate (aggregate and per-channel)
Sample rate is either specified as the aggregate rate (samples/second/aggregate) or the rate per channel (samples/second/channel).
Aggregate refers to the total number of points digitized from all channels per second, independent of the number of
channels being digitized;
whereas the later figure (s/sec/ch) refers to the number of samples digitized for each channel per second.
For example a 100,000 sample per second aggregate rate (100Ks/sec/aggregate) could refer to 1 channel at 100Ks/sec/ch or 4 channels
at 25K each (25Ks/sec/ch). If one specifies 25Ks/sec/ch, they are referring to 25K samples digitized
from each channel, independent of the number of channels digitized. See Also:
i240 and i4xx Maximum Sample RatesSample Rate Vs. Integration Time Vs. NoiseSetting Up A DigitizationUsing the instruNet World Strip Chart Recorder
18Maximum Multi-Channel Aggregate Sample Rate
Maximum multi-channel aggregate sample rate (samples/second/aggregate) refers to the maximum number of points digitized
from all channels (that are set up in a similar manner) per second, independent of the number of channels being digitized.
For example, if one sets up 10 thermocouple channels where the maximum specified multi-channel aggregate
sample rate is 1Ks/sec/ch, then the maximum rate for each channel would be 100 samples per second per channel.
If 100 channels were set up in this way, the maximum rate per channel would be 10s/sec/ch.
19Hardware Specifications Conditions
Specifications are maximum unless noted otherwise, ambient temperature is between 1 and 45°C, specifications are subject
to change without notice.
20i430 ±10V Measurement Range Supports Single-Ended Wiring (not differential)
The i430 provides software programmable single-ended or differential wiring for all voltage input ranges;
except ±10V, which is single-ended only.
21At Least One i43x A/D Module Must be Installed in Order to Measure Voltages
Many i4xx measurement modules do not contain an A/D converter, and therefore internally route measured voltages to an i43x A/D module
anywhere in the i4xx Card Cage (i.e. at least one i43x A/D module must be installed to measure voltages).
22Engineering Units
Engineering Units (EU) refers to the units commonly used with each sensor type. For example: engineering units are degrees C with
thermistor, RTD, and thermocouple measurements; ohms (Ω) with resistance measurements; Amps with current measurements;
and Volts with voltage measurements.
23Thermistor Sensor
instruNet connects directly to all types of thermistor's.
Thermistor devices are specified with several numbers. One is the thermistor resistance at 25°C (e.g. "2252 thermistor" refers
to a thermistor that is 2252Ω at 25°C); and the others are the Steinhart a/b/c coefficients. The later
describes the temperature vs. resistance curve for the device. instruNet software automatically calculates
these a/b/c coefficients when working with YSI/Omega 4xx or 4xxxx series thermistors; however, when working
with other manufacturers, one must obtain these coefficients from the manufacturer (or calculate them given
several temperature vs. resistance points) and then load them into the instruNet software.
For more details on how to set up non YSI/Omega 4xx or 4xxxx series thermistors (not related to i4xx cards), click
here.
24High Frequency Clock Output
When outputting a high frequency clock (e.g. > 500KHz), the output rise and fall time might not support the output frequency at full TTL levels.
To increase rise time, one can place an external pull up resistor (e.g. 1000 ohms) between 5Vpwr and the i/o pin (5V/1K = 5mA, 25mW).
With a 1K external pull up resistor, one can typically see ≤ 6MHz at TTL levels, and 24MHz at 400mVpp (e.g. 0.7V to 1.1V).
25i423 Channel Amplifier Buffered Outputs
Each of the six i423 differential input channels pass through their own amplifier,
where each has a
software selectable voltage gain of 1 or 64, and software selectable analog low pass filter;
as illustrated here.
After this treatment, the amplifier voltage outputs are made available at Hd44 connector
pins #17...22 for purposes of end user monitoring, in addition to possible internal
digitizing by A/D.
These outputs are short circuit protected against ±12Volts
power on or off; have a drive capability
of 3mA and 10K pF via an internal operational amplifier;
and have a maximum output working voltage of ±5Volts. These buffered
outputs are normally
off (0Volts output), and remain off until the end user has turned them on. This
can be done by setting
Channels #17...22 to ON from within instruNet World software (i.e. click on i423
Ch17..23 in NETWORK page and set Amplifier Output to ON), or writing ON (1=on, 2=off)
to those channel addresses
via software. The advantage of keeping them off is they are less likely to
couple into input signals
within the end user's cable.
26i100 Box
The i100 box is device that operates independently from the i4xx Card Cage.
27Route Power Directly Into i4xx/i100 Device
When routing power into an instruNet i4xx or i100 Device,
one should place the i300
power adaptor cable physically next to the i4xx Card Cage or i100 box, instead of next to the i2x0 controller card.
In other words, there should not be a DB25 cable between the i300 and the next device in the chain. The reason
for this is that power needs to travel on thick wires, else it incurs resistance, which leads to voltage drops along the Db25 cable.
28i4xx/i60x need i51x Wiring Box to measure thermocouple temperatures
Many i4xx/i60x products attach to
thermocouple sensors
and return temperature at the thermocouple tip, in °C units.
In order to do this measurement, the temperature of the screw terminals at the instruNet hardware must be known. The
i51x wiring box contains a temperature sensor just for this purpose.
Therefore, when working with thermocouples and i4xx/i60x, the thermocouple must be attached to the i51x
wiring box screw terminals, and the i51x must be bolted to the i4xx/i60x. The i100 box contains an internal
temperature sensor at screw terminals and therefore does not need an additional item in order to do thermocouple measurements.
2924bit A/D when Averaging for ≥ 1mSec
The i43x/i60x A/D Resolution is 24bits when averaging each point for ≥ 1mSec (i.e. Integration field set to ≥ 0.001 seconds); and 16bits when not averaging (Integration = 0).
Averaging is also referred to as “Integration” and it reduces the maximum sample rate,
as explained here. For more information on how to adjust Integration,
click here.
i60x products automatically support 24bit A/D resolution; whereas i4xx products only support 24bit if the "24bit A/D Support" field has been set to "i60x and i4xx" and one is working
with ≥ v3.6.0.11 software. To access the 24bit field, click the SETUP button in the RECORD page and then click the RECORD button.
30i60x supports three 120Ω gages or eight 350Ω gages i600/i601 products provide 80mA
of 3.3Vref power for strain gages and load cells. 120Ω gages draw
27mA (3.3V/120) and 350Ω gages draw 10mA (3.3V/350). Consequently, i60x products
are capable of powering ≤ 3 qty 120Ω gages or ≤ 8 qty 350Ω gages.
If one wants to connect > 3 qty 120Ω gages, consider
external power.
120Ω devices are typically not used due to excess heating at
the device (3.3V * 27mA = 90 mWatts). 350Ω devices
dissipate one-third as much heat (3.3V * 10mA = 33 mWatts).
31i601 is Electrically Isolated
The i601 product provides ±36V bank electrical isolation between measurement ground and computer ground. Alternatively, the less costly i600 directly connects I/O signal ground to computer ground via the USB cable.
32What is Included in the i60x Product Box
For a list of items included with the i60x product, click
here
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