Datasheet

 2015-2017 Microchip Technology Inc. DS20005426C-page 29
MCP9600
5.2.2 THERMOCOUPLE SENSOR
CONFIGURATION REGISTER
The MCP9600 Sensor Configuration register is used to
select the thermocouple sensor types and to select the
digital filter options. This device supports eight thermo-
couple types. Each type has a unique set of error
correction coefficients that are derived from the NIST
Thermocouple EMF Voltage Conversion database.
In addition, this device integrates a first order. recursive
Infinite Impulse Response (IIR) filter, also known as Expo-
nential Moving Average (EMA). The filter uses the current
new temperature sample and the previous filter output to
calculate the next filter output. It also adds more weight to
the current temperature data, allowing a faster filter
response to the immediate change in temperature. This
feature can be used to filter out fast thermal transients or
thermal instability at the thermocouple hot-junction
temperature. Writing this register resets the filter.
The filter equation is shown in Equation 5-4 and the
Filter Coefficient n is user-selectable, from Level 0 to 7.
A coefficient of 0 disables the filter function and a 7 coef-
ficient provides a maximum digital filter. Figure 5-6
shows the filter response to a step function, which can
be used to extrapolate the filter performance to various
temperature changes.
EQUATION 5-4: DIGITAL FILTER
FIGURE 5-6: Filter Step Response.
YkX  1k–Y
1–
 +=
Where:
Y = New filtered temperature in T
∆
X = Current, unfiltered hot-junction
temperatures
Y
-1
= Previous filtered temperature
n = User-selectable filter coefficient
k22
n
1+  =
0.0
0.5
1.0
0.0 32.0 64.0 96.0 128.0
Filter Output (°C)
Number of Temperature Samples
n=0
n=1
n=2
n=3
n=4
n=5
n=6
n=7
REGISTER 5-7: SENSOR CONFIGURATION REGISTER
U-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0
— Thermocouple Type Select, Type K, J, T, N, S, E, B, R — Filter Coefficients
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 7 Unimplemented: Read as ‘0’
bit 6-4 Thermocouple Type: Thermocouple Type Select bits
000 = Type K
001 = Type J
010 = Type T
011 = Type N
100 = Type S
101 = Type E
110 = Type B
111 = Type R
bit 3 Unimplemented: Read as ‘0’
bit 2-0 Filter Coefficient – n: Filter Coefficient bits
000 = n = 0: Filter off
001 = n = 1: Minimum filter
010 = n = 2
011 = n = 3
100 = n = 4: Mid filter
101 = n = 5
110 = n = 6
111 = n = 7: Maximum filter