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These numbers (8, 10 and 12 bits) refer to the measurement resolution available on the XR440 Data Logger. The XR440 converts analog signals (Temperature, Pressure, etc) into digital numbers. A digital number is a series of ones and zeros. An 8 digit (or 8 bit) digital number can represent 256 different values. A resolution of 8 bits means that the measurement range for each channel is divided into 256 parts. 10 bit resolution divides the measurement range into 1024 parts, and 12 bit resolution divides the measurement range into 4096 parts. The higher the number of bits, the finer the resolution, the higher the sensitivity (ability to measure small signal changes), and the more space required in memory to hold one reading. See Specifications to compare memory capacity and accuracy for 8, 10, and 12 bit resolution.
What resolution should I use?
In general, we suggest you select 12 bit resolution (in the software's Setup screen). The Setup screen displays the Total Log Time which is determined by the number of ON channels, the Sample Rate, and the selected Resolution. For a given setup, if a longer Total Log Time is desired, and a reduced sensitivity (resolution) is acceptable for your application, then you could select a lower Resolution, which would increase the Total Log Time (another way to increase the Total Log Time would be to change the Sample Rate).
How is memory allocated in the XR440 Data Logger?
The memory is evenly divided by the number of channels you have turned ON (in the software's Setup screen)
What is the function of the XR440's 'E' terminal?
The E terminal provides 5vdc excitation (power) to the PACE Temperature/Humidity Probe and all PACE Pressure Sensors.
Can the E terminal be used to power other non-PACE sensors?
In some cases, yes. The E terminal provides a precise 5 vdc at a maximum current of about 20 milliamps. If you are logging at a fast sample rate (1Hz - 200Hz) the E terminal output is a constant 5 vdc. However, if you are logging at a standard rate (2 secs or slower), the E terminal output is pulsed for a short time just prior to the XR440 sampling its inputs (either 0.025 secs or 0.1 secs, depending on the selected Setup). This is done to insure a long battery life. So even if your non-PACE sensor's power requirement is less than 20ma at 5vdc, it also needs a very fast warm-up time in order to work with the XR440.
Does using power from the E terminal reduce battery life?
If the total current drawn from the E terminal is less than 5 milliamps, battery life will be 2 - 3 years under normal use. Drawing 10 ma from the E terminal will reduce battery life to about 18 months, and 20 ma from the E terminal will reduce battery life to about 1 year. If Real Time Mode is used constantly, battery life will be cut roughly in half (see next question).
What is the effect on battery life if Real Time Mode is constantly active?
If you use Real Time Mode constantly, battery life will be cut approximately in half using the default 19.2k baud rate speed. Using slower speeds (9600 or lower) reduces battery life further and is not recommended if Real Time Mode is in constant use.
For linear sensors, how does the XR440's High / Low scaling compare to Slope / Offset scaling?
High / Low scaling is similar to Slope / Offset scaling. With High / Low scaling, the High value is the equivalent reading for a sensor output of 5v, and the Low value (and Offset value) is the equivalent sensor reading if its output is 0 volts.
High / Low scaling can be converted to Slope / Offset Scaling as follows:
Slope = (High Value + |Low Value|) / 5
Offset = Low Value
Note: |Low Value| is the absolute value of the Low Value; if the Low Value is a negative number, simply remove the negative sign, if it is positive, use the number as it is.
Slope / Offset scaling can be converted to the XR440's High / Low scaling as follows:
High Value = ( Slope * 5 ) + Offset
Low Value = Offset
Can Pace Pressure Sensors read in any unit of pressure?
Yes. Pace Pressure Sensors come with scaling values you key into Pocket Logger Software. The scaling values can be changed to read in any desired pressure unit (bar, kPa, etc). We have a calculator to convert the scaling values to a different unit of pressure.
XR440 Data Logger, Description and Pricing
Tel: (704) 799-0688 / Fax: (704) 799-0177 / e-mail: sales@pace-sci.com
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