HYDRA

Service Manual

Since virtually no current flows through the sense path, no error voltages are developed that would add to the voltage across the unknown resistance; this 4-wire measurement technique eliminates user lead-wire and instrument relay contact and circuit board trace resistance errors.

2-56. AC Volts

AC-coupled ac voltage inputs are scaled by the ac buffer, converted to dc by a true rms ac-to-dc converter, filtered, and then sent to the a/d converter.

Refer to Figure 2-6. Input HI is switched to the ac buffer by dc-blocking capacitor A3C31, protection resistor A3R11, and latching relay A3K15. Resistor A3R44 and A3K15 act to discharge A3C31 between channel measurements. LO is switched to the A3U8 A/D Converter through A3R34 and S18.

INPUT HI

A3R11

 

 

A3U6

 

 

 

 

A3K15

A3Z3

 

A3C15

 

 

&

 

 

1.111M

A3U7

 

 

A3C16

 

 

_

 

A3C31

+

 

RMS

 

 

COVERTER

 

 

 

 

A3Z3

 

A3R44

 

 

2.776k

 

 

 

 

 

 

A3Z3 FEEDBACK

A3Z3

 

 

RESISTOR

 

 

115.7

INPUT LO

 

 

 

A3R43

 

 

 

 

 

 

 

 

 

 

 

s6f.eps

Figure 2-6. AC Buffer Simplified Schematic

JFETs A3Q3 through A3Q9 select one of the four gain (or attenuation) ranges of the buffer (wide-bandwidth op-amp A3U7.) The four JFET drive signals ACR1 through ACR4 turn the JFETs on at 0V and off at -VAC. Only one line at a time will be set at 0 volts to select a range.

The input signal to the buffer is first divided by 10, 100, or 1000 for the 300 mV, 3V, and 30V ranges, respectively. The resistance ratios used are summarized in Table 2-6. Note that the 111.1-kΩresistor is left in parallel with the smaller (higher attenuation) resistors. The attenuated signal is then amplified by A3U7, which is set for a gain of 25 by the 2.776-kΩand 115.7Ω resistors in A3Z3. Components A3R27 and A3C23 compensate high-frequency performance on the 300 mV range. For the 300V range, overall buffer gain is determined by the ratio of the 2.776-kΩfeedback resistor to the 1.111-MΩinput resistor.

2-24

Page 71 Page 73
Page 72
Image 72
Fluke 2635A, 2625A service manual AC Volts
Page 71 Page 73

2635A, 2625A specifications

The Fluke 2625A is a sophisticated data logger designed for a wide range of industrial and laboratory applications. This versatile instrument excels in capturing and monitoring temperature and voltage measurements with precision and reliability. One of its standout features is its ability to record data from various sensors, making it ideal for environments where comprehensive data acquisition is critical.

Equipped with a large LCD display, the Fluke 2625A provides clear and user-friendly access to real-time measurement data. Its graphical interface allows users to visualize trends and monitor readings easily, which significantly enhances usability. The device supports a variety of input types and can connect to thermocouples, RTDs, and other sensors, offering great flexibility for various measurement tasks.

The Fluke 2625A employs advanced measurement technologies that ensure accuracy in data logging. With a high sampling rate, it captures fast-changing signals while maintaining data integrity. The device features a built-in memory that allows for extensive logging, accommodating long-term monitoring tasks without requiring constant oversight. Users can set it to log data at specified intervals, offering customizable solutions for different monitoring needs.

Another significant characteristic of the Fluke 2625A is its robust communication capabilities. The device supports USB and RS-232 interfaces for easy connectivity with computers and other devices, making data transfer and analysis seamless. This feature is especially beneficial for users who need to compile or analyze large sets of data quickly.

Furthermore, the Fluke 2625A is designed with durability in mind. Its rugged construction makes it suitable for challenging environments, including those with high levels of vibration, dust, or moisture. This reliability ensures that the device can withstand the rigors of fieldwork while still delivering accurate measurements.

In summary, the Fluke 2625A is a powerful data logger that combines versatility, accuracy, and reliability. Its user-friendly interface, advanced measurement technologies, and robust design make it an essential tool for professionals in various industries, from manufacturing and HVAC to research and development. Whether monitoring temperature changes in a laboratory or assessing voltage levels in an industrial setting, the Fluke 2625A stands out as a trusted solution for effective data logging and analysis.
Top Page Image Contents