Contract H0308041 

Design Engineering Laboratories, Inc. 

BUREAU OF MINES 

UNITED STATES DEPARTMENT OF THE INTERIOR 
DISCLAIMER NOTICE 

The views and conclusions contained in this document are those of 

the authors and should not be interpreted as necessarily representing 

the official policies or recommendations of the Interior Department's 

Bureau of Mines or of the U.S. Government. 
Development of a Closed Circuit TV Borehole Probe 

5m-m 

Se tember 1984 1'1 

Doug1 as Tall ey 3. Monnlng Orglnlxatbon Nmmr and Lddrua 

1 RoclprMs kuuhm Ma 

% Report W 

REPORT DOCUMENTATiON 

PAGE 

Design Enginnering Laboratories, Inc. 

2545 237th Street 

Torrance, CA 90505 

L RE*m I 

U.S. Bureau of Mines 

Department of the Interior 

Washington, D.C. 

4. 7itle mwd Subtltlr 

U-Trprollhoort&~~ 

Final Tecnni cal Report I 

-- - -- - 

l& Abstnct (Limrt: 200 words) 

This report describes a 4-inch diameter borehole probe which contains a low 

1 ight level TV camera, magnetic compass, light ill umination source, bottom/water 

detector sensor and a pointing angle sensor. The camera viewing angle is at a 

right angle to the probe's body. 

All data from the sensor is multiplexed into the closed circuit camera video 

for transmission on a single 50 ohm coaxial cable to a surface control unit. 

Likewise control of the probe's power, zoom lens, focus. panning and aperture is 

accompl i shed via a down-1 ink mu1 tip1 exed on the same cable. 

b 

17. - Arutysa8 a. Dlcrtg~om 

TV Borehole Probe, Downhole Data Link, Borehole TV Camera, Mulitplexed Data Link, 

Magnetic Compass Sensor, Downhole TV Tool 

IL wn~mg.rrErd.d Terms 

r cosn FWWG~~UO 

18. Avr4IaMltt-y Sbhrrnnt 19. f.cuwty Cbu CT)lh Repod 2l.Nadh.r 

Unclassified 22 m s-it~ a- rnh P.F) &wcm 

U~lassif~~ . . ANSC339.18) Sea lnrrrvakm on Rum- m rOrn 27ZtCT7) 

(FOmmriy ms3n DofmrbMnCdCornmrrrr 

3 
FORE WARD 

This report was prepared by Design Engineering Laboratories, Inc. under USBM 

Contract number H0308041. The contract was initiated under the Coal Mine 

Health and Safety Program. It was administered under the technical direction 

of PSMRC with Mr. Merle Bowswer acting as the original Technical Project 

Officer subsequently replaced by Mr. James Means. Mr. Mike Nowicki was the 

contract administrator for the Bureau of Mines. This report is a summary 

of the work recently completed as a part of this contract during the period 

December 1979 to September 1984. This report was submitted by the authors 

on September 1, 1984. 
TABLE OF CONTENTS 

Section Title 

INTRODUCTION 

TV CAMERA SYSTEM 

MULTIPLEX ELECTRONICS 

ILLUMINATOR ASSEMBLY 

COMPASS 

ROTOR ASSEMBLY 

TEST RESULTS/CONCLUSIONS 

Page 

7 

I. 4 

15 

19 

20 

21 

22 

1. INTRODUCTION 

This document presents the final report on the development of a "Closed 

Circuit TV Borehole Probe" which utilizes a low light level TV camera magnetic 

compass and a multiplex system to transmit video and data over a 1000 foot 

coaxial cable to an uphole control unit. 

1.1 Background 

Under this contract Design Engineering Laboratories (DEL) was given 

the task of developing a probe based on modifying an existing Bureau of Mines 

TV probe design to accomplish the following: 

a. Provide additional space for an improved low light level TV 

camera which was procured from Westinghouse and supplied to DEL 

by the Bureau of Mines. 

b. Add zoom lens capability. 

c. Add a magnetic compass and relative pointing angle sensor. 

d. Provide a mu1 tiplexed up1 ink/downl ink capabi 1 i ty to permi t transmi ssion 

of all video/sensor data and camera/probe controls on a single 

coaxial cable. This permits substantial reduction in the 

diameter and weight of the 1000 foot cable used with the probe. 

Drawings of the existing probe were supplied to DEL to utilize as the baseline 

design for the new probe. To minimize risk, minimum modifications to the 

existing design were desired. Hence most of the basic mechanical and 

packaging concepts were retained. The new probe was made 0.5 inches larger 

in diameter to provide additional space for the camera zoom lens. 

1.2 Probe Configuration 

Figure 1 shows the overall probe configuration which consists of five 

major modules or assemblies. These are: 
\ 

BOTTOM DETECT OR 

\ r FLOAT SWITCH 

CAP LAMP BAT1 

CABLE CONNECTOR 7 

CAP LAMP FLASHER ELECTRONICS 

SHAFT ENCODER 

ROTOR MOTOR 

POP-OFF SHUnER 

EXPLOSION PROOF WINDOW 

POP-OFF SHUTTER 

MOTORIZED LENS 

ELECTRONICS PACKING GLAND 

( EXPLOSION PROOF CHAMBER -----------LCC- 18' 

FIGURE 1. PROBE CONFIGURATION 
a. Rotor Assembly (See Figure 2) - This unit contains a DC motor, 

digital shaft encoder, main bearing, and cable connector to attach 

the probe to the main support cable. In normal operation this 

assembly remains stationary whi 1 e the main probe housing suspended 

below rotates 360 degrees driven by the DC motor. Limit stops 

are provided to prevent continuous rotation. 

b. Packing Gland (See Figure 2) - This assembly provides a protective 

barrier which feeds cables into the intrinsically safe portion of 

the probe. 

c. Battery Module (See Figure 3) - This area of the probe contains 

Ni-Cad batteries which operate the TV camera, pan motor, multiplex 

electronics, shaft encoder and compass. 

d. TV Camera/Mul tiplexer Unit (See Figure 4) - Contained in this 

module are the mu1 tiplex electronics packaged on three printed 

circuit boards and the TV camera, zoom lens and magnetic compass. 

e. Bottom Assembly (See Figure 5) - This assembly contains a bottom 

detector/float switch, cap lamp illuminator, pop-off shutter 

mechanism, lamp flasher electronics, batteries and folding mirror 

which deflects the camera line-of-sight at a right angle to 

probe longitudinal axis. 

Uphole control of the probe is accomplished with a 19 inch rack mount electronics 

assembly shown in Figure 6. This unit provides digital readout of the compass 

and rotor (shaft encoder) angles, provides manual controls for the iris, zoom 

lens, focus and pan motor, and provides three 75 ohm video outputs. 

Figure 7 shows the entire systems. 
FIGURE 3. BATTERY MODULE 
FIGURE 5. BOTTOM ASSEMBLY 
FIGURE 6. CONTROL UNIT 
FIGURE 7. CLOSED CIRCUIT BOREHOLE TV SYSTEM 
2. TV CAMERA SYSTEM 

The TV camera provided by the Bureau of Mines to DEL for use in the 

probe is a Westinghouse WTC34B-ISIT. This camera contains a one inch 

intensified silicon intensified tube which provides from 300 to 500 TV 

lines of resolution at faceplate illuminations of as little as 2 x 

foot candles. It operates from +12 VDC and provides a standard RS-170 

composite video output and a separate composite sync output. 

The camera's zoom lens is a CANON f2.5 with a zoom range of 18mm to 

108mm. The minimum object distance is approximately one meter. The f number 

is constant throught the entire zoom range. The motors for focus, iris 

opening and zoom range are located around the peripheral of the lens and use a 

friction type capstan drive to rotate the lens. Some obscuration of the 

f i e l d o f view is experienced at the lower focal range (18mm) due to the limited 

entrance aperture of the probe. 
3. MULTIPLEX ELECTRONICS 

Figure 8 is a block diagram of the overall electronic system. 

Power for the TV camera is provided through a relay by Ni-Cad 

batteries within the probe. The relay is energized by a 15 VDC bias signal 

which is applied to the cable through a 5 kilohm resistor in the uphole 

electronics. After power is applied to the camera it outputs composite 

video which is used as the synchronizing signal and clock for both the uphole 

and downhole electronics. 

Figure 9 shows the data format for both the uplink data and downlink 

data which is transmitted during the vertical interval of the video. Normal 

RS-170 video is composed of 525 horizontal lines which constitutes a complete 

frame of video. This frame is composed of two fields of 262.5 lines which are 

interlaced on the TV screen at a rate of 60 fields per second. For each field 

there are approximately 20 lines which are blank and do not contain any picture 

information. These lines do however contain the vertical sync pulse and 

will always be found at the top of the TV screen in the blanked vertical 

interval area. 

In the system which has been implemented lines 11 through 19 of the first 

field carry the downlink data while lines llthrough 18 of the second field 

carry the up1 ink data from the probe which consists of a1 ternate 8 bit samples 

from either the compass or theshaft encoder. The data is represented as the 

presence or absence ("1" or "0") of a high frequency tone burst (approximately 

2 mHz) which occupies one vertical line. Descriminators are used to detect 

the tone bursts and convert to logic levels c:ompatible with the rest of the low 

power CMOS logic used in both the uphole and downhole multiplex electronics. 
--- --- 

I DOWN HOLE ELECTRONICS 

COMPOSITE 

SYNC t-----s 

SHAFT ENCODER 

PAN MOTOR INHIBIT 

TO CAMERA 

AND DATA LIN

I-

FIGURE 8. ELECT
PAN PAN FOCUS FOCUS IR18 IRIS ZOOM ZOO

+/- WW */- WW */- O)(/- */- OWO

FiCSTNLEIE - WHITE 

D~SPUYEDON k- DoWNUNK DATA scRED( - BLACK 

DISPUYOD ON - 

SCREEN 

U 

/ SHm ENCODER 

OR COMPASS DATA 

I-, UPLINK DATA - 

FIGURE 9. TYPICAL DATA FORMAT 
The downlink data is defined as follows: 

a. Pan +/- 

Determines direction of pan motor rotation. 

b. Pan On/Off 

Enables or disables pan motor. 

c. Focus +/- 

Determines NEAR/FAR focus di rection. 

d. Focus On/Off 

Enables or disables focus motor. 

e. Iris +/- 

Determines OPEN/CLOSE direction of iris motor. 

f. Iris On/Off 

Enables or disables IRIS motor. 

g. Zoom +/- 

Determines IN/OUT direction of zoom lens. 

h. Zoom On/Off 

Enables or disables zoom motor. 

i. Hag/Rotor 

This is a synchronizing signal which is used to select 

either magnetic compass data or shaft encoder data to be 

transmi tted uphole on a1 ternate uphole transrni ssions. 

The uphole data consists of 8 bits (A7 through AO) of either magnetic compass 

data or shaft encoder data which is transmitted alternately during field 2 

of each video frame or 15 times a second for each eight bit word. Each of the 

8 bit words is converted into an analog voltage and displayon on separate 

digital panel meters which are scaled to readout in degrees. 
4. ILLUMINATOR ASSEMBLY 

Downhole illumination is provided by a standard miner's cap lamp 

which is mounted in the lower portion of the probe below the TV camera. This 

cap lamp is battery powered from Ni-Cad cells mounted with the lamp. Also 

contained in this module is a flasher module which causes the lamp to flash 

for 10 seconds at a one second rate every time a float switch/bottom detector 

switch is actuated in the bottom of the probe. This notifies the operator 

that the probe has reached the bottom of the hole or is in water. The flasher 

circuit is a typical one shot which only actuates once per bottom switch 

closure permitting the probe to rest on the bottom or in water without 

flashing the lamp. 

When the float switch/bottom detector is first closed a motor is actuated 

which removes a plexiglass protective shutter which covers the camera's aperture. 

This pop-off shutter is required to prevent build-up of mud on the camera lens 

and folding mirror during the lowering of the probe down the borehole. 
1 5. COMPASS 

The compass is a Digicourse Model 218 which outputs an 8 bit digital 

Gray code word representative of the heading. This 8 bit word is 

transmitted uphole with the multiplexed shaft encoder data. 

In the uphole electronics the Gray code word is converted to an 8 bit 

binary word which is in turn converted to an analog voltage by a digital to 

analog converter. This analog voltage is scaled and displayed on a panel 

meter as 0 to 360 degrees. 

When the probe is used in cased boreholes or in the vicinity of large 

amounts of ferrous metals, the shaft encoder is used with known reference 

points or landmarks to determine camera pointing. 
6. ROTOR AS:SEMBLY 

To maintain compatibility, the same rotor motor manufactured by 

TRW/GLORE which was used on the original probe is used on this probe. The 

rotor section also contains hard mechanical stops to prevent rotation greater 

than 360 degrees of the probe in the event of an electronic failure. Prior 

to impacting these mechanical stops electrical deactivation of the motor 

will normally occur. The circuitry which implements these stops is contained 

in the downhole electronics and uses the shaft encoder as a sensor to determine 

when to deactivate the motor. Uphole a similar circuit is used to illuminate 

a set of panel lamps when either the right or left stop has been reached. 

The shaft encoder is manufactured by LI'TTON and outputs 9 bits of angle 

information. The normal Gray code angle data is converted inside the encoder 

to a binary format by an internal TTL circuit. The most significant 8 bits 

of the data are selected to be transmitted uphole. A digital to analog 

converter converts this 8 bit parallel word into an analog voltage which is 

scaled and displayed on a digital panel meter as an angle up to 360 degrees. 
7. TEST RESULTS/CONCLUSIONS 

Results of test performed at Design Engineering Laboratories showed 

the LLTV to be remarkably sensitive even under conditions of very low 

illumination. It seemed to he well suited for the intended application. 

The multiplex system performed its task of transferring the data 

with low drop out or error rate. Its only observed defect was an 

occassional momentary data drop-out during sudden high frequency transients 

of the video which could be caused by rapidly covering and uncovering the 

entire camera aperture with a lens cap. Under normal operating conditions 

no such problems were observed. 

The compass, rotor assenibly and cap lamp flasher operated without 

incident. 

The zoom lens mechanism operated properly but required careful adjustment 

to achieve satisfactory performance. These adjustments consisted of setting 

the proper tension between rubber drive rings on the lens and the capstan 

on the drive motors. Too little tension and the lens would not rotate smoothly; 

too much tension and the motor would occassional ly stall. After initially 

attempt.ing to perform these ad justments with shims, set screws were provided 

for each motor which provide the required degree of precision to set the 

tension properly. If the probe is used frequently (i.e. once a day) these 

adjustments may require attention to compensate for wear of the rubber/capstan 

drive. At the time the zoom lens was developed no commercially available 

motorized zoom lens could be obtained which would fit into the 3.5 inch I.D. 

housing. Late in the program Lennox Instrument. proposed a custom direct 

replacement lens which should be considered as a possible improvement for 

the existing probe or future versions.