Attention: Retained for backward compatibility onlyas of v 2.7. This is used only in the waveform message, CHM category, which has been retained for backward compatibility only in v 2.7.
HL7 Component Table - CD - Channel Definition
| Core Framework | Base Standard Profile | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Seq# | Description | Interpretation | Flags | Cardinality | Length | C.LEN | Vocabulary | Data Type | Implement | Cardinality | Vocabulary |
 CD |
|||||||||||
 1 |
Channel Identifier | [0..1] | WVI | ||||||||
| 2 |
Waveform Source | [0..1] | WVS | ||||||||
| 3 |
Channel Sensitivity and Units | [0..1] | CSU | ||||||||
| 4 |
Channel Calibration Parameters | [0..1] | CCP | ||||||||
| 5 |
Channel Sampling Frequency | [0..1] | NM | ||||||||
 6 |
Minimum and Maximum Data Values | [0..1] | NR | ||||||||
Definition: This data type is used for labeling of digital waveform data. It defines a recording channel, which is associated with one of the values in each time sample of waveform data. Each channel has a number (which generally defines its position in a multichannel display) and an optional name or label (also used in displays). One or two named waveform sources may also be associated with a channel (providing for the use of differential amplifiers with two inputs). The other components of the channel definition data type are optional. The individual components are defined as follows:
Definition: This component specifies the number and name of the recording channel where waveform data is transmitted.
Definition: This component identifies the source of the waveform connected to the channel. Two names may be specified if it is necessary to individually identify the two inputs for a waveform. Only one name need be specified if the channel is connected to a single input. For example, in EKG recordings typically only one name is used (such as I or II); in electroencephalography, two names are typically used, one for each input of the differential amplifier (such as F3 and C3).
Definition: This component defines the channel sensitivity (gain) and the units in which it is measured.
Definition: This component identifies the corrections to channel sensitivity, the baseline, and the channel time skew.
Definition: This component defines the sampling frequency in hertz of the channel, that is, the reciprocal of the time in seconds between successive samples
Definition: This component defines the minimum and maximum data values which can occur in this channel in the digital waveform data, that is, the range of the ADC. , and also specifies whether or not non-integral data values may occur in this channel in the waveform data. If the minimum and maximum values are both integers (or not present), only integral data values may be used in this channel. If either the minimum or the maximum value contains a decimal point, then non-integral as well as integral data values may be used in this channel. For an n-bit signed ADC, the nominal baseline B = 0, and the minimum (L) and maximum (H) values may be calculated as follows:
L = -2n-1
H = 2n-1 - 1
For an unsigned n-bit ADC, the minimum value L = 0, and the nominal baseline value (B) and maximum value (H) may be calculated from the formulas,
B = 2n-1
H = 2n - 1
The actual signal amplitude A (for differentially amplified potential measurements, the potential at electrode number one minus that at electrode number two) may be calculated from the value D (range L to H) in the waveform data using the actual baseline value B and the nominal sensitivity S and actual sensitivity correction factor C by the formula,
A = SC(D-B)
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