Device Ordering Options
Calibrated output resolution can be ordered to be 16, 17, or 18 bits.
Higher resolution results in slower update times; see the Data Update Time in the Performance Characteristics table.
Parylene Coating: Parylene coating provides a moisture barrier and protection form some harsh media. Consult factory
for applicability of Parylene for the target application and sensor type.
The DLH is a digital sensor with a signal path that includes a sensing element, a variable- bit analog to digital converter,
a DSP and an IO block that supports either an I2C or SPI interface (see Figure 1 below). The sensor also includes an
internal temperature reference and associated control logic to support the configured operating mode. Since there is a
single ADC, there is also a multiplexer at the front end of the ADC that selects the signal source for the ADC.
Figure 1 - DLH Essential Model
The ADC performs conversions on the raw sensor signal (P), the temperature reference (T) and a zero reference (Z)
during the ADC measurement cycle.
The DSP receives the converted pressure and temperature information and applies a multi-order transfer function to
compensate the pressure output. This transfer function includes compensation for span, offset, temperature effects on
span, temperature effects on offset and second order temperature effects on both span and offset. There is also
linearity compensation for gage devices and front to back linearity compensation for differential devices.
Sensor Commands: Five Measurement commands are supported, returning values of either a single pressure /
temperature reading or an average of 2, 4, 8, or 16 readings. Each of these commands wakes the sensor from Idle state
into Active state, and starts a measurement cycle. For the Start-Average commands, this cycle is repeated the
appropriate numper of times, while the Start-Single command performs a single iteration. When the DSP has
completed calculations and the new values have been made available to the I/O block, the sensor returns to Idle state.
The sensor remains in this low-power state until another Measurement command is received.
After completion of the measurement, the result may then be read using the Data Read command. The ADC and DSP
remain in Idle state, and the I/O block returns the 7 bytes of status and measurement data. See Figure 2, following. At
any time, the host may request current device status with the Status Read command.
See Table 1 for a summary of all commands.
For optimum sensor performance, All Sensors recommends that Measurement commands be issued at a fixed interval
by the host system. Irregular request intervals may increase overall noise on the output.
Furthermore, if reading intervals are much slower than the Device Update Time, using the Averaging commands is
suggested to reduce offset shift. This shift is constant with respect to time interval, and may be removed by the applica-
tion. For longer fixed reading intervals, this shift may be removed by the factory on special request.
I/O Interface Configuration: The sensor automatically selects SPI or I2C serial interface, based on the following protocol:
If the /SS input is set low by the host (as occurs during a SPI command transaction), the I/O interface will remain
configured for SPI communications until power is removed. Otherwise, once a valid device address and command have
been received over the I2C interface, the I/O interface will remain configured for I2C until power is removed.
NOTE: The four-pin (SIP) packages only support the I2C interface.
DLH Series Low Voltage Digital Pressure Sensors