Rainbow-electronics DS1859 Manual de usuario descargar pdf (Pagina 10)

DS1859

Dual, Temperature-Controlled Resistors with

Internally Calibrated Monitors

10 ____________________________________________________________________

Monitored Signals

Each signal (V

, MON1, MON2, MON3, and tempera-

ture) is available as a 16-bit value with 12-bit accuracy

(left-justified) over the serial bus. See Table 1 for signal

scales and Table 2 for signal format. The four LSBs

should be masked when calculating the value.

For the 20kΩ version, the 3 LSBs are internally masked

with 0s.

The signals are updated every frame rate (t

frame

) in a

round-robin fashion.

The comparison of all five signals with the high and low

user-defined values are done automatically. The corre-

sponding flags are set to 1 within a specified time of

the occurrence of an out-of-limit condition.

Calculating Signal Values

The LSB = 100µV for V

, and the LSB = 38.147µV for

the MON signals when using factory default settings.

To calculate V

, convert the unsigned 16-bit value to

decimal and multiply by 100µV.

To calculate MON1, MON2, or MON3, convert the

unsigned 16-bit value to decimal and multiply by

38.147µV.

To calculate the temperature, treat the two’s comple-

ment value binary number as an unsigned binary num-

ber, then convert to decimal and divide by 256. If the

result is greater than or equal to 128, subtract 256 from

the result.

Temperature: high byte: -128°C to +127°C signed; low

byte: 1/256°C.

SIGNAL

+FS

SIGNAL

+FS

(hex)

-FS

SIGNAL

-FS

(hex)

Temperature 127.984°C 7FFC -128°C 8000

6.5528V FFF8 0V 0000

MON1 2.4997V FFF8 0V 0000

MON2 2.4997V FFF8 0V 0000

MON3 2.4997V FFF8 0V 0000

Table 1. Scales for Monitor Channels at

Factory Setting

SIGNAL FORMAT

Unsigned

MON1 Unsigned

MON2 Unsigned

MON3 Unsigned

Temperature Two’s complement

Table 2. Signal Comparison

TEMPERATURE

(°C)

CORRESPONDING LOOK-UP

TABLE ADDRESS

<-40 80h

-40 80h

-38 81h

-36 82h

-34 83h

——

+98 C5h

+100 C6h

+102 C7h

>+102 C7h

Table 3. Look-up Table Address for

Corresponding Temperature Values

MSB 2

LSB 2

MSB (BIN) LSB (BIN) VOLTAGE (V)

10000000 10000000 3.29

11000000 11111000 4.94

-1

-2

-3

-4

-5

-6

-7

-8

MSB (BIN) LSB (BIN) TEMPERATURE (°C)

01000000 00000000 64

01000000 00001111 64.059

01011111 00000000 95

11110110 00000000 -10

11011000 00000000 -40

MSB (BIN) LSB (BIN) VOLTAGE (V)

11000000 00000000 1.875

10000000 10000000 1.255

Monitor/V

Bit Weights

Temperature Bit Weights

Monitor Conversion Example

Conversion Examples

Temperature Conversion Examples

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 27 28

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