
Electronic 
Theodolites
PENTAX Industrial Instruments Co.,Ltd.
2-5-2 Higashi-Oizumi / Nerima-ku, Tokyo 178-0063,Japan
Tel.+81-3-5905-1222 / Fax +81-3-5905-1225
E-mail:international@piic.pentax.co.jp
ETH-302 
ETH-305 
ETH-310
Instruction manual
Total Construction Solutions
10 sec.Angle Accuracy 
Detachable Tribrach
5 sec.Angle Accuracy 
Detachable Tribrach
2 sec.Angle Accuracy 
Detachable Tribrach
ETH-320
20 sec.Angle Accuracy 
Detachable Tribrach

3
Safety Precautions (must be followed)
The following items are intended to prevent possible injury to the user or 
other people and/or damage to the instrument before it occurs. 
These safety precautions are important to the safe operation of this 
product and should be observed at all times.
•
Distinctive Displays
The following displays are used to distinguish precautions by the 
degree of injury of damage that may result if the precaution is ignored.
WARNING
Items indicated by this display are precautions which if ignored could 
result in death or serious injury.
CAUTION
Items indicated by this display are precautions which if ignored may 
result injury or material damage.
• Here ”injury” refers to injuries such as cuts, burns or electric shock 
the treatment of which will not likely require hospitalization or 
long-term attention.
• ”Material damage”refers to the damage to facilities,buildings, 
acquired data, etc.
WARNING
• Never look at the sun through the telescope as this may result in loss of  
sight.
• Do not use at a place near flammable materials as there will be a risk of 
fire or injury by explosion.

4
CAUTION
• Secure the handle of main unit with the handle locking screws.
Failure to properly secure the handle could result in the main unit 
detaching from the handle while being carried, causing injury.
• Do not use the carrying case as a footstool as it is slippery and 
unstable and may cause you to fall, resulting in possible injury.
• When mounting the instrument to the tripod, tighten the center 
screw securely.Failure to tighten the screw properly could result 
in the instrument falling off the tripod causing injury.
• Securely tighten the leg fixing screws of the tripod. A person 
could be injured by the tripod shoes on an extending leg due 
to a loose screw.
• Do not carry a tripod with the metal shoe pointing toward another 
person as the person may be injured if they strike them.
• Make sure that your hands and feet are not in the vicinity of 
the tripod legs when setting up the tripod, or a hand or foot stab 
would occur.
• Do not wield or throw the plumb bob. A person could be 
injured if struck.
• If a battery box or a battery is gets wet by water, wipe off the 
water and dry immediately.
• When a battery box is removed from the unit, power must be off. 
If the battery box is removed with power on, it will cause trouble.
Electro-Magnetic Compatibility(EMC) 
This instrument complies with the protection requirement for 
residential and commercial areas. 
If this instrument is used close to industrial areas or transmitters, 
the equipment can be influenced by electromagnetic fields.

5
CONTENTS
•1.General 7
1.1 Precautions
1.2  Standard equipment
1.3  Names of Parts
1.4  Preparation of power
•2.Key Operations and Display 14
2.1 Display
2.2  Keyboard
2.3  Function of each key
2.3.1  Power on-off key
2.3.2  V/% key
2.3.3  Hold key
2.3.4  0 set key
2.3.5  R/L key
2.3.6  Illumination key
2.4  Other functions
2.4.1  Remaining battery indicator
• 3. Special Key Operations 22
3.1  Setting of vertical angle
3.2  Setting of 90°buzzer
3.3  Setting of correction of vertical angle
3.4  Setting of angle measurement
3.5  Setting of automatic power-off function
3.6 Setting of Angle unit
•4.Preparation for Surveying 28
4.1  Setting up the instrument
4.2  Leveling with the circular vial
4.3  Leveling with the plate vial
4.4  Centering with the optical plummet
4.5  Eyepiece adjustment
4.6  Object sighting

6
CONTENTS
•5.Measurement 34
5.1  Horizontal angle measurement (right)
5.2  Horizontal angle measurement (left)
5.3  Vertical angle measurement
•6. Inspection and Adjustment 37
6.1  Instructions on inspection and adjustment
6.2  Perpendicularity of plate vial to vertical axis
6.3  Perpendicularity of circular vial to vertical axis
6.4  Inclination of reticule graduations
6.5  Perpendicularity of line of sight to horizontal axis
6.6  Difference of the vertical angle
6.7  Optical plummet
•7. Optional Accessories 44
7.1  Diagonal eyepiece
•8.Specifications 45

7
1. General
1.1 Precautions
Storing and environmental conditions
• Do not use the instrument until it has adjusted to 
the ambient temperature.
• Avoid using at a high or low temperature.
The instrument may not work normally at 
temperatures exceeding –10 or +50˚C.
• When the instrument gets wet,
wipe off the water immediately and let it completely dry 
outside of the case. Store in the case after completely dried.
• Be sure to store instrument in the case. Avoid storing in a place that is 
subject to high temperature, high humidity, or dust.
• When not in use for extended periods, remove a battery from the 
battery box. Also remove the instrument from the case and expose 
to the air periodically.
Battery
• Batteries can naturally discharge due to shipment time.
Use new batteries for the first job.
• The four (4) batteries, in a battery box, should be of the same type.
• Do not use batteries, in a battery box, which have different remaining 
capacities.
• Do not touch the liquid of leaking batteries.

8
Transportation
• Do not subject to impact or vibration during 
transportation.
• When transporting, handle the same as ”fragile” and
pack the shipping case with cushioning materials.
Inspection, Adjustment and Repair, Overhaul
• When not in use for extended periods of having been subjected to 
impact or vibration, be sure to check the instrument adjustments 
before using.
• If there is any problem in the instrument,
do not attempt to repair or you may make 
the problem worse. 
Contact your local dealer for proper repair or instructions.

9
Others
• When cleaning the case or the instrument, do not use any organic 
solvent.The surface of plastic parts may dissolve and deformation 
and discoloration can occur. 
Wipe off the dirt with a wet cloth of dilute household detergent
• Wipe off dirt on the optics with a cleaning cloth (or paper) specified 
for optical surfaces.
• To realize full capability of the instrument, adhere to 
cautions described in each chapter of this manual.
1.2 Standard Equipment
• Body (with objective cap)
• Battery box (One battery box is installed in the instrument)
• Batteries* (Contained in the carrying case)
• A set of tools (Adjusting pin, driver)
• A plumb bob
• Rain cover
• Carrying case
• Instruction manual
*The standard equipment AA batteries can naturally discharge due to 
shipment time. Use new batteries for the first job. 
When disposing used batteries, please follow your municipal 
government rules.

10
Unpacking and Storing 
Unpacking
• Gently set down the carrying case so that its cover is upward.
• Unlatch and open the case while pushing the latch lock.
• Take the instrument out of the case.
Storing
• Set the telescope almost horizontal, and lightly tighten the telescope 
clamp screw.
• Align the containing marks*, and lightly tighten the horizontal clamp 
screw.
• Insert the instrument into the case with the containing marks* 
facing upward.
• Close the case lid and lock the latches.
*Containing mark = Yellow dot sticker

13
1.4 Preparation of Power
• Remove battery box from the unit by pushing the release button on 
the top of the battery box. Remove the battery box cover.
• Insert four AA batteries into the battery box according to (+) and (-).
• Press the battery box to the leg by inserting the guide pin 
to the guide groove.
• Confirm the correct work by pressing the power switch.
This instrument can operate using 1.2V AA rechargeable batteries.
• The four (4) batteries, in a battery box, should be of the same type.
Do not use batteries, in a battery box, which have different remaining 
capacities.
• When a battery box or batteries are wet, wipe off the moisture 
immediately and dry completely.
• When a battery box is removed from the unit, power must be off.
If the battery box is removed with power on, it will cause trouble.

14
2. Key Operations and Display
2.1 Display
Ver tical angle 
V=Zenith 0°, V%=Slope(VH=Horizontal 0°, Vc=Compass)
Horizontal angle  Battery indicator: 
(HR=right rotation horizontal angle, HL=left rotation horizontal angle)
2.2 Keyboard
[V/%] key 
(Switches the display of vertical angle)
[R/L] key  (Set the horizontal angle right 
and left rotation alternately)
[HOLD] key (Pressing twice holds the horizontal 
angle shown on the display)
[0SET] key (Pressing twice resets the horizontal angle to 0°,00’,00”)
[    ]Illumination key (Illuminate LCD panel and the telescope reticle)
[ON/OFF] key
(Turns the power on and off alternately)

15
2.3 Function of each key
2.3.1 Power [ON/OFF] key
<Power ON and set the vertical angle 0 point> 
Pressing the ON/OFF key turns on the power supply and the message 
”0 SET” is displayed. After the ”0 SET” of vertical angle is performed, 
the Horizontal and Vertical angle are displayed and the instrument 
enters into the angle measurement mode.
<Setting vertical angle 0 point> 
Set the vertical angle 0 point by turning the telescope upward or 
downward when the instrument is at the ”normal” position 
(Vertical circle at left.)
<Power OFF> 
To turn the power supply off,press the ON/OFF key for more than 
1 second (”OFF” will display) and then release it. Power turns OFF.
1
2
3

16
2.3.2 [V/%] key
Pressing the V/% key will change the Vertical angle display to 
V%(slope). (At the shipping, it is set at Zenith 0°)
By special key operation, horizontal 0° (VH) and Compass (Vc) 
can be set. 
(Factory default is Zenith 0°) 
(Refer to 3.1 Setting of vertical angle.)

17
The error ”OVER RANGE” is displayed when the telescope 
exceeds 45°(100%) in the V% display mode.

18
2.3.3 [HOLD] key
Press the [HOLD] key twice in succession to hold the displayed 
horizontal angle and retain it. (Press once, the key buzzer will sound, 
then press again during the sound.) 
Press the key once more to release.
To prevent operation error, the buzzer sounds for three seconds 
when the [HOLD] key is pressed. 
HOLD is not initiated unless the key is pressed during 
the buzzer sound.
1
2

19
2.3.4 [0SET] key
Press the [0SET] key twice in succession to reset the displayed 
horizontal angle 0°,00’,00”.(Press once, the key buzzer will sound, 
then press again during the sound.) 
Press the key once more to release.
To prevent operation error, the buzzer sounds for three seconds when 
the [OSET] key is pressed. 
[OSET] is not initiated unless the key is pressed during the buzzer 
sound.
1
2

20
2.3.5 [R/L] key
Press the [R/L] key to change from clockwise to counterclockwise 
rotation. A clockwise or counterclockwise reading is alternately 
displayed each time the key is pressed.
Clockwise horizontal angle Count horizontal angle in a right 
rotation direction (HR)
Counterclockwise horizontal angle Count horizontal angle in a left 
rotation direction (HL) 
If the power turns off during the counterclockwise mode, the display 
returns to a clockwise horizontal angle display when power is turned on.
2.3.6 [Illumination key    ]  
Pressing the    key, illuminates the LCD panel and telescope reticule. 
The illumination is automatically turned off after five minutes. 
Pressing the key, with illumination on, turns off the illumination.
1
2

21
2.4 Other Functions
2.4.1 Remaining battery indicator
The status of the remaining battery capacity is displayed with 
””symbolizing the battery capacity.
Battery full - operating possible 
Operation possible 
Operation still possible 
Get the battery ready for a stand by 
Replace batteries
Automatic Power-off function 
If there is no key operation for about 30 minutes, the power supply is 
turned off automatically. 
This function can be set to NIL by special key operation. (Refer to 3.5 
Setting of automatic power off function.)

22
3. Special key operations
Special key operation enables selection of angle unit and 
other such items.
Press [HOLD] key and [0SET] key at the same time
Press [ON/OFF] key
Release [ON/OFF] key
(No display or buzzer) 
Release [HOLD] key and [0SET] key,
Following display appears:
1
2
3
4
5

23
Flow of setting display
Setting of vertical angle
Press [R/L] key
Setting of 90°buzzer
Press [R/L] key
Setting of correction of vertical angle 
Press [R/L] key
Setting of angle display
Press [R/L] key
Setting of automatic power off function
Press [R/L] key
Setting of Angle unit
Previous items can be displayed by pressing the [HOLD] key.

24
3.1 Setting of Vertical Angle
Ver tical angle setting display by special key operation
Zenith 0° (V) 
Setting is switched by pressing [0SET] key
Horizontal angle 0°(VH)
Compass (Vc)
Store with [V/%] key when the setting is decided.

3.2 Setting of 90°buzzer
90°buzzer setting display by special key operation
No 90°buzzer
Setting is switched by pressing [0SET] key 
With 90°buzzer 
Store with [V/%] key when the setting decided.
3.3 Setting of correction of vertical angle
Correction of vertical angle setting display by special key operation
Setting is switched by pressing [0SET] key
Store with [V/%] key when the setting decided.
25

26
3.4 Setting of angle measurement
Angle setting display by special key operation
For models ETH-302/305
Setting is switched by pressing [0SET] key 
Store with [V/%] key when the setting decided.
For models ETH-310
Setting is switched by pressing [0SET] key 
Store with [V/%] key when the setting decided.
For ETH-320
Setting is switched by pressing [0SET] key 
Store with [V/%] key when the setting decided.
1
2
3

27
3.5 Setting of automatic power off function 
Automatic power off function setting display by special key operation
Automatic power off active
Setting is switched by pressing [0SET] key
Automatic power off inactive
Store with [V/%] key when the setting decided.
3.6 Setting of Angle unit
Setting is switched by pressing [0SET] key
You can Select DEG or DEC or GRD or MIL as the unit for angle.
Store with [V/%] key when the setting decide.

28
4. Preparation for Surveying
4.1 Setting up the instrument
Adjust the tripod legs so that a height suitable for surveying is 
obtained when the instrument is set on the tripod. 
A Set the tripod and fix the metal shoe firmly into the ground so that 
the tripod head is as level as possible and centered above the station 
point. If the tripod head is disturbed by the action of fixing the metal 
shoe into the ground, correct the level by extending or retracting each 
leg of the tripod. 
Set the instrument on the tripod head; insert the tripod center screw 
into the instrument bottom plate and tighten firmly.
1
2
3
Tripod head
Center screw
Trip od 
Bottom plate

29
4.2 Leveling with the Circular level
After [4.1 Setting up the instrument] is completed, instrument must be 
leveled using the circular vial.
By rotating any two leveling screws,position the bubble in the center 
of the vial (See A.) (To adjust the screws at the same time, turn them in 
opposite directions.) 
Adjust the remaining leveling screw,and position the bubble in the 
center of the circle (See B) 
For the relation between the screw adjusting direction and bubble 
moving direction, refer to the arrows of the following figures. Bubble will 
move to the right in figure A, while in figure B it moves upward.
1
2
(A) (B)

30
4.3 Leveling with the Plate level
After [4.2 Leveling with the circular vial] is completed,instrument must be 
leveled with plate vial.
Place the plate vial in parallel with a line joining any two of the leveling 
screws. By rotating two leveling screws in the opposite direction of 
each other,position the bubble in the center of the vial (See A) 
Rotate the plate vial through 90°, position the bubble in the center of 
the vial by operating the remaining one leveling screw (See B) 
Confirm if the bubble stays in the center by rotating the 
instrument 180°. 
If the bubble moves, repeat procedure    and   .
For the relationship between the screw adjusting direction and bubble 
moving direction, refer to the arrows of following figures. Bubble will 
move to the left in figure A, while in figure B moves upward.
When the bubble is not positioned in the center by repeating procedure   
and    in procedure 4.2 , adjustment is required.
(Refer to [6.Inspection and Adjustment.])
1
2
3
1
2
1
2
(A) (B)
Plate vial

31
4.4 Centering with the optical plummet
After [4.3 Leveling with the plate vials] is completed,the instrument must 
be centered above the station point.
Focus the optical plummet reticule by rotating the optical plummet 
eyepiece knob. 
Focus the station point by rotating the optical plummet focusing knob. 
Loosen the tripod center screw.Look through the optical plummet 
eyepiece, and move the instrument bottom plate until the reticule 
center coincides with the station point. (Take care not to rotate 
the instrument) 
Tighten the tripod center screw.Ascertain that the bubble stays 
positioned in the center when rotating the plate vial position in steps 
of 90°. If the bubble is not positioned in the center, adjust with the 
leveling screws. (Refer to [4.3 Leveling with the plate vial]).
Even if the bubble is shifted by one graduation in  , deviation of 
centering is just 0.3mm, at the instrument height of 1.4m,giving little 
effect on the survey result.
1
2
3
4
Center mark
4

32
4.5 Eyepiece adjustment
After [4.4 Centering with the optical plummet] completed, focus the 
telescope eyepiece on the telescope reticule.
Remove the telescope lens cap. 
Point the telescope at a bright object. 
Rotate the eyepiece completely counterclockwise. 
Look through the eyepiece, and rotate the eyepiece clockwise until the 
reticule appears at its maximum sharpness.
At procedure , keep your eye relaxed to prevent parallax and eye 
fatigue. Parallax causes problems with object sighting. 
(Refer to [4.6 Object sighting]) 
1
2
3
4
Horizontal graduation
(double)
Ver tical graduation
(single)
Ver tical graduation
(double)
Optical axis
Reticule pattern
4

33
4.6 Object sighting
After [4.5 Eyepiece adjustment] is completed, sight the object.
Loosen the telescope clamp screw and horizontal clamp screw. 
Point the telescope at the object using the collimator sight. 
Tighten the telescope clamp screw and horizontal clamp screw. 
Focus on the object by rotating the focusing ring, while looking 
through the telescope. 
Accurately align the reticule with the object, using each tangent 
screw.
• In procedure , focus on the object correctly so that the reticule 
will not move in relationship to the object when you move your eye 
slightly left and right, while looking through the eyepiece.
• Turn the focusing ring clockwise to focus on a near object.
Turn the focusing ring counterclockwise to focus on a far object.
• Two screws of the collimator are fixed and adjusted at the distributor 
or the manufacturer.Do not move them arbitrarily.
1
2
4
5
3
Horizontal clamp screw
Horizontal tangent screw
object
Focusing ring
Telescope eyepiece
Collimator
4

34
5. Measurement
5.1 Horizontal angle measurement (right)
Level the instrument, and after power on set the vertical angle 0 point. 
Sight the first object using the horizontal clamp and tangent screw as 
well as the telescope clamp and tangent screw. 
Press [0SET] twice to set the horizontal angle to 0°,00’,00” 
Sight the second object using the horizontal clamp and tangent screw 
as well as the telescope clamp and tangent screw. 
Read the displayed value (α).
First Object: Zero Setting (0 °00’ 00”)
Second Object (34 °47’ 20”)
Horizontal Angle (α) = 34 °47’ 20”
1
2
4
5
3
First object
Second object

35
5.2 Horizontal angle measurement (left)
Level the instrument, and after the power on set 
the vertical angle 0 point. 
Sight the first object using the horizontal clamp and tangent screw as 
well as screw as well as the telescope clamp and tangent screw. 
Press the [R/L] key to switch the horizontal angle display to 
counterclockwise reading (HL).
Subsequent operation will be done as in [5.1 Horizontal angle 
measurement (right), but the order of collimation is reversed.
To switch the mode back to ”right”,press the [R/L] key again.
• If the power turns off during the counterclockwise mode, the display 
returns to a clockwise horizontal angle display when power is 
turned on.
2
1
3

36
5.3 Vertical angle measurement
Level the instrument, turn the power on and set 
the vertical angle 0 point. 
Sight the object A using the horizontal clamp and tangent screws as well 
as the telescope clamp and tangent screws.
Read the displayed value (  ).
• The vertical angle mode can be changed to slope percent display 
(V%) by pressing [V%] key. 
Also, horizontal 0°(VH) and compass (Vc) can be set using special 
key operation. 
(Factory setting is Zenith 0°) 
(Refer to 3.1 Setting of vertical angle)
Ver tical angle (θ) = 86 °24’40” 
Press the [V/%] key to view the Vv and V%.
Ver tical angle 0 point
Object
Horizontal angle

37
6. Inspection and Adjustment
6.1 Instructions on inspection and adjustment
• Inspection and adjustment should be done after setting the 
instrument on a tripod or on an adjustment stand.
• Inspection should be done sequentially from [6.2 Plate vial] to 
[6.5 Perpendicularity of line of sight to horizontal axis] 
• Adjustments should be finished with adjustment screws having been 
tightened and with firm torque. Do not finish by loosening an 
adjustment screw.
• Repeat inspection after adjustment and confirm if the adjustment is 
performed correctly.
• It is recommended that a trained professional perform adjustments,
if possible.
6.2 Perpendicularity of plate vial to vertical axis
Inspection
Perform [4.3 Leveling with the horizontal vial] 
Rotate the instrument through 90° and confirm if the bubble is 
always in the center. 
When the bubble is in the center,no adjustment is necessary. 
If the bubble moves from the center, following adjustment is required.
1
2
3
Leveling screw
Plate vial

38
Adjustment
Center the plate vial bubble. 
Rotate the instrument 180°, move the bubble half way back to 
the center by operating a leveling screw which is located parallel 
with the plate vial. 
Rotate the vial adjusting screw with the adjusting pin and position 
the bubble in the center. 
Repeat procedure again to confirm.
1
2
3
4

39
6.3 Perpendicularity of circular vial to vertical axis
Inspection
Confirm if the bubble of the circular vial is in the center after 
the inspection and adjustment of [6.2 Plate vial]. 
No adjustment is necessary if the bubble of the circular vial is 
in the center but if not, the following adjustment is required.
Adjustment
Move bubble to the center by rotating the bubble adjusting 
screws, using the adjusting pin. 
Inspect again.
1
2
1
2
Circular vial
Bubble adjusting screws

40
6.4 Inclination of reticule graduations
Inspection
Set an object point A on the line of sight through the telescope. 
Move point A to the edge of the field of view by adjusting the 
telescope tangent screw (point A’). 
No adjustment is necessary if point A moves along the vertical line of 
the reticule. If the point A does not move along the vertical line of the 
reticule, it needs adjustment - Consult with your dealer.
1
2
3
Ver tical line
Line of sight axis

41
6.5 Perpendicularity of line of sight to horizontal axis
Inspection
Set an object (point A) at a distance of 30 to 50m away from the 
instrument and sight it through the telescope. 
Loosen the telescope clamp screw and reverse the telescope around 
the horizontal axis. Mark a point set on the line of sight at about the 
same distance to the object point A, and call it point B. 
Loosen the horizontal clamp screw, and rotate the instrument around 
the vertical axis. Sight point A again. 
Loosen the telescope clamp screw,and reverse the telescope around 
the horizontal axis. Mark a point on the line of sight at about the same 
distance as point B, and call it point C. 
No adjustment is necessary if point B and C coincide, 
but if it does not - Consult with your dealer.
1
2
4
5
3

42
6.6 Difference of the vertical angle
Inspection
Set the vertical angle in Zenith 0° mode 
Sight an object (Point P) with the telescope and read the vertical 
angle (V correct). 
Reverse the telescope and rotate the alidade. 
Sight point P again in the reverse position and 
read the vertical angle (V reverse). 
At this time, when (V correct + V reverse - 360°)/2 is less than 15”, 
it is within tolerance. If it shows a larger value, 
it needs adjustment - Consult your dealer.
1
2
4
5
3

43
6.7 Optical plummet
Inspection
Place a piece of white paper,with a cross drawn on it,directly under 
the instrument. 
Look through the optical plummet, and move the paper so that the 
intersecting point of the cross comes to the center of the field of view. 
Adjust the leveling screws so that the center mark of the optical 
plummet coincides with the intersection point of the cross. 
Rotate the instrument around the vertical axis. Look through the 
optical plummet each step of 90° rotation, and observe the center 
mark position against the intersection point of the cross. 
If the center mark always coincides with the intersection point, no 
adjustment is necessary.When it does not coincide,the following 
adjustments are required.
Adjustment
Remove the cover of the optical plummet. 
Mark the point set on the line of sight at each step of 90° on the 
white paper and call them A,B, C and D. 
Join the opposed points (A, C and B, D) with a straight line,and set 
intersecting point 0. 
Turn four optical plummet adjusting screws with the adjusting pin so 
that the center mark coincides with the intersection point 0. 
Repeat procedure again to confirm.
Optical plummet adjusting screw
5
1
2
3
4
5
1
2
3
4
Cap of optical plummet
Adjusting pin for the center mark

44
7. Optional Accessories
7.1 Diagonal Eyepiece (SB14)
The Diagonal eyepiece can be attached to the telescope for convenience 
in observing the zenith or when in confined spaces.
<Installation>
Turn the telescope eyepiece ring counterclockwise to remove 
the eyepiece. 
Be sure to hold the eyepiece, securely,so that you do not drop it. 
Attach the diagonal eyepiece to the telescope by reversing 
the procedure.
The diagonal eyepiece can be rotated through 360°.
When sighting through the telescope with the diagonal eyepiece 
attached, the reticule may be seen deflected vertically or horizontally, 
but this has no influence upon accuracy.
1

45
8. Specifications
Telescope
Magnification 30 X 
Effective aperture  45 mm 
Resolving power  3” 
Field of view  1° 30’ 
Minimum focus distance 1.35 m 
Stadia ratio 100 
Stadia constant 0
Angle Measurement
Type          Incremental rotary encoder 
Detection mode  V. angle: Single
H. angle: Dual
Minimum Display (Selectable)
ETH-302 1”/5” 
ETH-305 1”/5” 
ETH-310 5”/10” 
ETH-320 10”/20”
Accuracy (DIN18723, Standard deviation)
ETH-302 2” 
ETH-305 5” 
ETH-310 10” 
ETH-320 20”
Ver tical Angle Compensation
Method          Automatic compensation
Stadia Ratio 100 
Stadia Constant 0  
Display
Type Dot matrix LCD/Two lines 
Display panel Dual display

46
Ver tical axis  
Single
Sensitivity of vials
Plate vial
ETH-302 30”/2 mm  
ETH-305 30”/2 mm 
ETH-310 40”/2 mm 
ETH-320 40”/2 mm
Circular vial 8’
Tribrach type        
Detachable
Optical plummet
Magnification 3 x 
Focusing range 0.5 m to Infinity
Power source
Type 4 x AA dry battery 
Operation time (Alkaline) 25 to 28 hrs.
(NiMH2300mAh) 25 to 28 hrs.
Water resistant
IP x4
Ambient temperature
- 10 °C to + 50 °C
Height
215 mm
Dimensions
Instrument (including batteries) W168 x H330 x L158mm/4.6kg

certified
Printed in Belgium
Member s ym bol of the Japan Surveying 
Instruments Manufacturers’ Association 
representing the high quality surveying 
products.
2-5-2 Higashi-Oizumi
Nerima-ku, Tokyo 178-0063,Japan
Tel.:+81-3-5905-1222
Fax: + 81-3-5905-1225
E-mail:international@piic.pentax.co.jp
PENT
AX Industr
ial Instr
umen
The CE marking assures that 
this product complies with 
the requirements of the EC 
directive for safety.
ts C
o., Lt
d.