Geokon 8020-59, Instruction Manual

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1. INTRODUCTION
The Model 8020-59 Vibrating Wire (VW) to Analog Converter is a low cost module that
provides a simple way to connect Geokon’s vibrating wire transducers to data acquisition
systems that are not capable of reading frequency signals nor able to generate the proper signals
required to excite VW transducers. The converter can operate with single transducers, as a stand-
alone device, or with multiple transducers in conjunction with the Geokon Model 8032
Multiplexer. The converter is powered using either a 12V or a 24V supply.
The 8020-59 interface is capable of outputting a 0-5V or 4-20mA signal that is directly
proportional to “digits”, a vibrating wire sensor’s native units. These outputs are easily converted
to digits via several simple formulas (see Section 4.3). The analog outputs are automatically
scaled to minimum and maximum parameters (defaults are 0 and 25,000) and sloped to provide
their complete 0-5V or 4-20mA range for each individual transducer. These analog outputs offer
20-bit resolution (one part in 1,048,576) with an accuracy of better than 0.1% of full scale span
(0-5V output) throughout the operating temperature range (-20 ºC min, +80 ºC max). In a similar
fashion, the temperature reading from the transducer’s thermistor is available with 10-bit
resolution (one part in 1024). When configured for single-channel operation, the 8020-59
updates the reading approximately once every second.
Pin
Number
Signal
Name
Signal Description
1 GND Analog Signal Ground
2 V OUT Conversion Voltage Output, 0 to 5 Volts
3 +24V 24 Volt Power In
4 +24V GND Ground for 24V Power
5 I-RET Return for Conversion Current Output
6 +12V 12 Volt Power Supply In OR +12V Output, if powered by 24V
7 GND Ground for 12 Volt Power
8 TH+ Thermistor Positive Lead
9 TH- Thermistor Negative Lead
10 C+ Vibrating Wire Positive Lead
11 C- Vibrating Wire Negative Lead
12 VALID Valid Output:
5V indicates conversion complete
0V indicates conversion not done
13 ENABLE Enable Input:
Single Channel Mode: 0V = VW output (digits)
5V = Temperature output (˚C)
16/32-Channel Mode: 0V = Conversion Disabled
5V = Conversion Enabled
14 CLOCK Clock Input:
Single Channel Mode: 0V = 8020-59 ON
5V = 8020-59 OFF
16-Channel Mode: 0
→ 5V transition =
increment channel and select VW Analog or Temperature Analog
32-Channel Mode:
0 → 5V transition = increment channel
15 I-OUT VW and Thermistor Conversion Current Output
Table 1 - Connector Pinout and Signal Description