NJM4151D Datasheet NJM4151D | P10-P12

NJM4151

Ver.2012-10-24

3. A/D Converter

One example is to connect the microprocessor to analog converter output. A / D converer is required are as follows.

Good noise rejection, high stability, low cost. Many industrial systems are sufficient for an 8-bit⋅1/256.

A typical

microprocessor works with 8-bit input. Data from the AD converter should be parallel with TTL logic levels. Digital data

should be controlled by logic input.

Typically, the input is called STATUS. Request conversion rate depends on applied

field. Digital voltmeter is converted into digital signals per second to 2.3 times.

AD converter for the radar pulse must be

converted within 100 nanoseconds. AD converter can be configured with a parallel 8-bit output by using the NJM4151.

If the slow conversion of the AD converter by using the NJM4151, noise removal is good, better linearity and better

isolation can be configured at low cost. Also, you can easily increase the degree of decomposition. If you use the

NJM4151, the conversion time is 1s to 10ms. Please refer to Figure 10. Single-digit or further of NJM4151 will be coupled

to the counter through a photo coupler.

Figure 10. Connect to Micro Processor

In many applications, the counter circuit / timing make time division for each channel. Photo coupler is not absolutely

necessary. Help to separated the counter / timing circuit and VF-encoder. Thus, VF encoder does not matter even if the

contact point away. Therefore, can be used in distance away from the microprocessor.

Encoder output pulse train must be parallel to the digital signal. The 8-bit counter is set to 0.

Then, only a fixed time to

count the pulses from the encoder. Condition that the gate is ON, the counter is only for the specified duration. The higher

the input voltage to the encoder, the encoder output frequency is higher. The digital readout of the counters at the end of

a certain duration will be directly proportional to the input frequency. To make the best operating, the duration and the

encoder scale factor recommend choose to become the maximum count of 255(as an 8-bit binary) at maximum input

voltage.

Figure 11 is a data conversion system of N channels. A number of transducers is coded each by VFC. N-channel

multiplexer is coupling to 8-bit counter. At that time, any one of the encoder output go through with photo-coupler.

Channel selection method is as follows. Microprocessor, or manually enter the address of the digital. Timing will be

performed by a number of different things. The most accurate way is as follows. It is to be used as a low-frequency by

dividing high frequency with the accurate high frequency crystal oscillator. A similar method, it attached divider circuit to a

tuning fork oscillator . The most inexpensive way to make the timing is as follows. It is way to drive a one-shot use the

optocouplers from the line voltage for AC. Maximum error is less than 0.5% so AC voltage is about 0.2% in most

areas.Please note that this method is affected because of the AC line transient response. In addition, NJM555 (Timer IC)

can also be used in the astable mode.

Positiv

/Negativ

Voltag

Tranc

Deuc

Nch

V/F Converte

nd Multiplication

Optical coupled

Isolator

Timing

and

Counter

8bit

parallel

output

micro

processor

NJM4151

Ver.2012-10-24

Figure 11. Multi channel ADC system

Figure 12 shows 1-channel ADC. Commercial power supply frequency has been used to generate the timing. NJM556

(Dual timer IC) is used to strobe and reset pulse generator. Latch circuit is the same as the output data of a counter circuit

when the strobe pulse is high level. The counter data is latched when the strobe pulse is a low level.

Figure 12. 8-bit ADC system (for 1-channel)

Positiv

/Negativ

Voltag

Optical

coupled

Isolator

Optical

coupled

Isolator

Trance Deuce 1

Commercial power

/ Timer

Timing watch

Single stable multi and Timing circui

Reset

8bit

counter

8bit

latch

from computer

Digital output

MUX address

separated pulse

common

frequency

N channel multiplexer

V/F N channel encode system

Commercial power

Single stable multi

Reset

Counter

Latch

Digital output

Trance Deuc

Commercial

power

frequency output

convetor

Encode common

for encode common

for computer common and counter circuit common

NJM4151

Ver.2012-10-24

This pulse is used to the microprocessor status monitor. After the counter output is latched, the counter is reset by a

reset pulse. Then becomes the first status again. This alternate get started the counter under the action of

microprocessor instructions. The best logic sequence is determined by individual applications. To illustrate the calculation

of the scale factor, try to assume the resolution of 8 bits at 1 / 60 s convert time. Maximum output will be 1+2+4+8+16+

32+64+128=255. The maximum output frequency is 255 × 60Hz, and 15.3kHz.

Accuracy and stability of the ADC is determined by NJM4151 (VFC) chip, an external R,C components, and the timing

circuit. Please discuss the error at the following contents: offset, scale factor, linearity, noise. Please consider that there is

uncertainty of ± 0.195% for to put into the prediction error. The approximate ADC has linearity error of ± 1 / 2 LSB at

corresponding to ± 0.195%. NJM4151 can easily design by linearity of ± 0.05% or linearity of ± 0.1%. Most of linearity is

not an issue. Offset drift is determined by input offset drift of the external OP-AMP. So in most cases is very small. The

largest source of error are gain drift of NJM4151, and temperature coefficient of external R,C components. NJM4151 has

a gain drift of 100ppm / °C average approximately. Error goal of 100ppm / °C can be improved by choosing the external

components very well. At 200ppm / °C stability of the timing, gain drift of the total will be 400ppm / °C. This is the

maximum gain variation of 2.8% at 70°C from 0°C. If the ADC gain drift is too high, you should try and see the power of

the microprocessor. Coupled to the input of the VFC at the reference value of zener diodes of low drift at periodically. To

calculate the gain error, impress the digital value of the supplied reference voltage to microprocessor and memory circuit.

It is easy. The correct term of scale factor calculated is used to correct gain drift.

The computer can be used to remove noise. It is time and again to convert the same signal voltage. Next, remove the

ones far off the average. Then calculate the average. Using computer technology to all of these applications are not

required. However, it is often used to improve the accuracy of the system without increasing the cost of the hardware set.

NJM4151 is achieved ADC by a very low cost channel. The accuracy of the system conforms to the resolution of the 8-bit.

If necessary, Computer receives the data conversion will reduce in many errors. It can be used to improve the overall

accuracy of the system.

4. ADC for proportional meter

The accuracy of the systems is better on used proportional method, for measurement equipment. Use the NJM4151,

Figure 13 shows the proportion by weight measurement system. First, the strain gauge bridge circuit, and the cells of

weight detecting detect the weight. Then generates a difference voltage. The Difference voltage (VD) for the converting

bridge approximated VB∆R / RT in a small range of resistance changes of strain - gauge. Necessary information is ∆R /

RT and the voltage (VB) across the bridge must be stable. Instrumentation - amplifier amplify the low input differential

voltage (VD). It is used to eliminate the common mode input voltage. The voltage across the bridge (VB) converted to

frequency (fB). Then, the output voltage amplitude (V0) converted to frequency (f0). Hereby, ADC is designed for

proportional meter. The voltage across the bridge converter is 1Hz / V. Amplifier voltage converter is 1kHz / V conversion

factor. Proportional counter and frequency meter type of proportional will be used to convert frequency ratio f0/fB. The

first advantage of conversion technology by the proportional method is that it is independent of the voltage across the

bridge. Frequency (fB) is proportional to the bridge voltage (VB). Output frequency (f0) is proportional to the VB. f0/fB is

independent of VB, only proportional to ∆R / RT.

Figure 13. Proportional meter system

Instruments Amplifier

Parallel Digital Output

Proportional

Frequency

Meter

Proportional

Counter

Converter

1kHz/V

Scale

-10V Typical value

Read Span 000 to 999

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15

NJM4151D

Mfr. #:

Buy NJM4151D

Manufacturer:

NJR (New Japan Radio)

Description:

Voltage to Frequency & Frequency to Voltage V-F/F-V Converter

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet

NJM4151D