Introduction - Geokon 8020-59 Instruction Manual

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 Signal
Number Name
1
2 V OUT
3
4 +24V GND
5 I-RET
6
7
8
9
10
11
12 VALID
13 ENABLE
14 CLOCK
15 I-OUT
Signal Description
GND Analog Signal Ground
Conversion Voltage Output, 0 to 5 Volts
+24V 24 Volt Power In
Ground for 24V Power
Return for Conversion Current Output
+12V 12 Volt Power Supply In OR +12V Output, if powered by 24V
GND Ground for 12 Volt Power
TH+ Thermistor Positive Lead
TH- Thermistor Negative Lead
C+ Vibrating Wire Positive Lead
C- Vibrating Wire Negative Lead
Valid Output:
5V indicates conversion complete
0V indicates conversion not done
Enable Input:
Single Channel Mode: 0V = VW output (digits)
16/32-Channel Mode:
Clock Input:
Single Channel Mode: 0V = 8020-59 ON
16-Channel Mode:
increment channel and select VW Analog or Temperature Analog
32-Channel Mode:
VW and Thermistor Conversion Current Output
Table 1 - Connector Pinout and Signal Description
5V = Temperature output (˚C)
0V = Conversion Disabled
5V = Conversion Enabled
5V = 8020-59 OFF
0 → 5V transition =
0 → 5V transition = increment channel
1