Yamato BM500 User manual

Water Bath
BM500/510
Oil Bath
BO400/410
Instruction Manual
- Fourth Edition -
Yamato Scientific Co. LTD.,
This paper has been printed on recycled paper.
zThank you for purchasing "Water Bath, BM / Oil
Bath, BO Series" of Yamato Scientific Co., Ltd.
zTo use this unit properly, read this "Instruction
Manual" thoroughly before using this unit.
Keep this instruction manual around this unit for
referring at anytime.
WARNING!:
Carefully read and thoroughly understand the
important warning items described in this
manual before using this unit.

Contents
1.Cautions in Using with Safety.............................................................1
•Explanation.................................................................................................................... 1
•Table of Illustrated Symbols .......................................................................................... 2
•Fundamental Matters of "WARNING!" and "CAUTION!" ............................................... 3
2.Before Using This Unit.........................................................................5
•Requirements for Installation......................................................................................... 5
•Installation Method ........................................................................................................ 8
•Preparations for Operation............................................................................................ 9
3.Description and Function of Each Part............................................12
•Main Unit ..................................................................................................................... 12
•Control Panel............................................................................................................... 13
•Characters of the Controller ........................................................................................ 14
4.Operation Method ..............................................................................15
•Operation Mode and Function List .............................................................................. 15
•Operation Mode, Function Setting Key, and Characters ............................................. 17
•Fixed Temperature Operation...................................................................................... 18
•Quick Auto Stop Operation.......................................................................................... 19
•Auto Stop Operation.................................................................................................... 21
•Auto Start Operation.................................................................................................... 23
•Setting of Overheating Prevention Device .................................................................. 25
•Key Lock Function....................................................................................................... 26
•Bath Operation Setting Function ................................................................................. 26
•Calibration Offset Function.......................................................................................... 27
•Reparation Function at Power Failure......................................................................... 28
5.Handling Precautions ........................................................................29
6.Maintenance Method..........................................................................31
•Daily Inspection and Maintenance .............................................................................. 31
7.Long storage and disposal................................................................32
•When not using this unit for long term / When disposing ............................................ 32
•Environmental protection should be considered ......................................................... 32
8.In the Event of Failure…....................................................................33
•Safety Device and Error Code..................................................................................... 33
•Trouble Shooting ......................................................................................................... 34
9.After Service and Warranty ...............................................................35
•In Case of Request for Repair..................................................................................... 35
10.Specification.....................................................................................36
11.Wiring Diagram.................................................................................37
12.Replacement Parts Table.................................................................39
13.Reference..........................................................................................40
14.Installation Standard Manual...........................................................41

1
1.Cautions in Using with Safety
Explanation
MEANING OF ILLUSTRATED SYMBOLS
Various symbols are used in this safety manual in order to use the unit without
danger of injury and damage of the unit. A list of problems caused by ignoring
the warnings and improper handling is divided as shown below.Be sure that you
understand the warnings and cautions in this manual before operating the unit.
WARNING! If the warning is ignored, there is the danger of a problem that
may cause a serious accident or even fatality.
CAUTION! If the caution is ignored, there is the danger of a problem that may
cause injury/damage to property or the unit itself.
Meaning of Symbols
This symbol indicates items that urge the warning (including the caution).
A
detailed warning message is shown adjacent to the symbol.
This symbol indicates items that are strictly prohibited.
A
detailed message is shown adjacent to the symbol with specific actions not to
perform.
This symbol indicates items that should be always performed.
A
detailed message with instructions is shown adjacent to the symbol.
Illustrated Symbols
(Note 1) Serious injury means a wound, an electrical shock, a bone fracture or intoxication that may
leave after effects or require hospitalization of outpatient visits for a long time.
(Note 2) Minor injury means a wound or an electrical shock that does not require hospitalization o
r
outpatient visits for a long time.
(Note 3) Property damage means damage to facilities, devices and buildings or other properties.

2
1.Cautions in Using with Safety
Table of Illustrated Symbols
Warning
Warning,
generally
Warning,
high voltage
Warning,
high temperature
Warning,
drive train
Warning,
explosive
Caution
Caution,
generally
Caution,
electrical shock
Caution,
scald
Caution,
no road heating
Caution,
not to drench
Caution,
water only
Caution,
deadly poison
Prohibit
Prohibit,
generally
Prohibit,
inflammable
Prohibit,
to disassemble
Prohibit,
to touch
Compulsion
Compulsion,
generally
Compulsion,
connect to the
grounding
terminal
Compulsion,
install on a flat
surface
Compulsion,
disconnect the
power plug
Compulsion,
periodical
inspection

3
1.Cautions in Using with Safety
Fundamental Matters of "WARNING!" and "CAUTION!"
WARNING!
Do not use this unit in an area where there is flammable or explosive gas
Never use this unit in an area where there is flammable or explosive gas. This unit is not explosion-proof.
An arc may be generated when the power switch is turned on or off, and fire/explosion may result. (Refer to
page 409 "List of Dangerous Substances".)
Always ground this unit
Always ground this unit on the power equipment side in order to avoid electrical shock due to a power surge.
Ban on operation when an abnormality occurs
If smoke or strange odor should come out of this unit for some reason, turn off the circuit breaker right away,
and then disconnect the power plug. If this procedure is not followed, fire or electrical shock may result.
エラ
ー!
リン
クが
正し
くあ
りま
せ
ん。
Do not use the power cord if it is bundled or tangled
Do not use the power cord if it is bundled or tangled. If this procedure is not followed, fire or electrical shock
may result.
Do not process, bend, wring, or stretch the power cord forcibly
Do not process, bend, wring, or stretch the power cord forcibly. Fire or electrical shock may result.
Perform periodic check
Check the device frequently. Do not leave the dust and dirt on the wiring terminals and electrical
components. A fire disaster may result in.
Never use an explosive or a flammable material with this unit
Never use explosive substances, flammable substances and substances that include explosive or flammable
ingredients in this unit. Explosion or fire may occur. (Refer to page 40 "List of Dangerous Substances".)
Do not touch high-temperature parts
The inside of the body or the door may become hot during and just after operation. It may cause burns.
Do not disassemble or modify this unit
Do not disassemble or modify this unit. Fire or electrical shock or failure may be caused.
CAUTION!

4
During a thunder storm
During a thunderstorm, turn off the power key immediately, then turn off the circuit breaker and the main
power. If this procedure is not followed, fire or electrical shock may be caused.
When electric power failure occurs…
The device stops operation when electric power failure occurs. In this case, turn off the breaker for safety.

5
2.Before Using This Unit
Requirements for Installation
WARNING!
1. Always ground this unit
•Be sure to connect the ground wire to the earth conductor or earth terminal to prevent
accidents caused by an electric shock.
•Do not connect the earth wire to gas or water pipes. If not, fire disaster may be caused.
•Do not connect the earth wire to the ground for telephone wire or lightning conductor. If not,
fire disaster or electric shock may be caused.
•Use the receptacle with exclusive earth terminal for the BM500 and B0400 models which ha
large capacity with single-phase 100V to 120V specification.
•Use the receptacle with exclusive earth terminal for the BM510 and B0410 models with
single-phase 200V to 240V specification.
2. Choose a proper place for installation
•Do not install this unit in a place where:
♦Rough or dirty surface.
♦Flammable gas or corrosive gas is generated.
♦Ambient temperature above 35°C.
♦Ambient temperature fluctuates violently.
♦There is direct sunlight.
♦There is excessive humidity and dust.
♦There is a constant vibration.
♦There is not exhauster and ventilator.
•Make sure that no flammable substances are placed around the devices. Keep space as
shown, at least, in the figure below.
More than
10cm
More than
10cm
More than 10cm
More than 10cm
Main Unit

6
2.Before Using This Unit
Requirements for Installation
WARNING!
3. Do not use this unit in an area where there is flammable or explosive gas
•Never use this unit in an area where there is flammable or explosive gas. This unit is not
explosion-proof. An arc may be generated when the power switch is turned ON or OFF, and
fire/explosion may result.
•To know about flammable or explosive gas, refer to page 40 “List of Dangerous Substances”.
4. Requirements for Installation
For BO400 and BO410 models…
The oily smoke of silicon oil generated by heating is flammable and may cause fire
disaster.Silicon oil also may generate harmful gas when it reaches a high temperature. Be
sure to install an exhauster, ventilator and extinguisher around the device.
×
Extinguisher
Exhauster and ventilator

7
2.Before Using This Unit
CAUTION!
5. Do not modify
Modification of this unit is strictly prohibited. This could cause a failure.
6. Installation on horizontal surface
Place this unit as flat a place as possible. If the rubber feet are not in uniform contact with
the floor surface, noise or vibration may result. Additionally, the unit may cause a problem or
malfunction.
7. Choose a correct power distribution board or receptacle
•Choose a correct power distribution board or receptacle that meets the unit’s rated electric
capacity.
Electric capacity: BM500/BO400: 100 to 120V AC, 12.5A
BM510/BO410: 200 to 240V AC (single phase), 6.5A
NOTE)
There could be the case that the unit does not run even after turning ON the power. Inspect
whether the voltage of the main power is lowered than the specified value, or whether other
device(s) uses the same power line of this unit. If the phenomena might be found, change the
power line of this unit to the other power line.
8. Before/after installing
•It may cause injure to a person if this unit falls down or moves by the earthquake and the
impact. etc..To prevent, take measures that the unit cannot fall down, and not install to busy
place.
•Be sure to install an exhauster, ventilator and extinguisher around the device.
Modification

8
2.Before Using This Unit
Installation Method
9. Handling of power code
1.Warning
•Do not entangle the power cord. This will cause overheating and possibly a fire.
•Do not bend or twist the power cord, or apply excessive tension to it. This may cause a fire
and electrical shock.
•Do not lay the power cord under a desk or chair, and do not allow it to be pinched in order to
prevent it from being damaged and to avoid a fire or electrical shock.
•Keep the power cord away from any heating equipment such as a room heater. The cord's
insulation may melt and cause a fire or electrical shock.
•If the power cord becomes damaged (wiring exposed, breakage, etc.), immediately turn off the
power at the rear of this unit and shut off the main supply power. Then contact your nearest
dealer for replacement of the power cord. Leaving it may cause a fire or electrical shock.
•Connect the power plug to the receptacle which is supplied appropriate power and voltage.
2. Power cord connection
Connect power supply plug into power
cord surely when to connect unit.
Use of power cord overseas
Use the power cord that meets the
safety standard of relevant countries
when the device is used overseas.
Use the attached power cord (rated current: 15A).

9
2.Before Using This Unit
Preparations for Operation
Precautions at operation for water bath BM500 and BM510
Be careful about the followings at the operation of device.
①Connect the power to the receptacle which has sufficient capacity left.
②Do not move the device during the operation.
③Be careful not to burn yourselves during operation of device.
④The temperature inside the bath and device, especially on the edge of bath, is high during and after
the operation. Do not touch them with bare hands.
⑤Do not drain the device until the water temperature falls to 45℃or below.
⑥Do not spill water over the installation area of water bath on the main body when feeding water.
The insulation failure or ground leakage may result in.
⑦Do not perform unmanned operation.
⑧Use water as medium. Ion-exchange water is recommended to be used to prevent adhesion of
calculus.
⑨Do not operate the device in the open air.
⑩Turn off the power when removing the water bath from the main body.
⑪Do not heat the bath without water in it.
Precautions at operation for oil bath BO400 and BO410
Be careful about the followings at the operation of device.
①Connect the power to the receptacle which has sufficient capacity left.BO400: AC100 to 120V for
power supply voltage/approx. 12.5A for current capacity.BO410: AC200 to 240V for power supply
voltage/approx. 6.5A for current capacity.
②Do not move the device during the operation.
③Be careful not to burn yourselves during operation of device.
④The temperature inside the bath and device, especially on the edge of bath, is high during and after
the operation. Do not touch them with bare hands.
⑤Do not drain the device until the oil temperature falls to 45℃or below.
⑥Do not spill oil over the installation area of oil bath on the main body when feeding oil. The
insulation failure or ground leakage may result in.
⑦Do not perform unmanned operation.
⑧Use silicon oil as medium. Do not use the other liquid other than it.
⑨Do not operate the device in the open air.
⑩Turn off the power when removing the oil bath from the main body.
⑪Do not heat the bath without oil in it.
⑫Be careful not to overflow the oil during heating.

10
2.Before Using This Unit
Preparations for Operation
Fluid medium for oil bath BO400/BO410
The maximum operating temperature of BO400/410 model oil bath is 180℃.
Select the silicon oil used only for heat transfer medium, with heat resistance and open system
(heat-resistant dimethyl silicon oil) having the viscosity of 50 ㎜2/s (cSt) or less.
Recommended silicon oil:
200℃or below for operating temperature, Made by Toshiba Silicon Co., Ltd. TSF458-50
Manufacturer Toshiba Silicon
Recommended temperature 200℃or below
Product name TSF458-50
Appearance Light yellow, transparent
Specific gravity (25℃) 0.961
Viscosity (25℃) ㎜2/s (cSt) 50
Volatile (150℃，24h)% 0.3
Temperature coefficient of viscosity 0.59
Ignition point (℃) 325
Fluid point (℃) -50℃or below
Characteristics of silicon oil
Rate of increase in viscosity (300℃, 168h)% 40
The deterioration speed of silicon oil (viscosity change) varies depending on the operating temperature.
Please inquire with the manufacturer of silicon oil for details at the time of purchase.
Water/oil amount supplied to in-bath
The maximum amount of fluid (water/silicon oil) at heating should be approximately 30 mm or less from
the upper end of in-bath with the sample flask being sunk into the fluid.
Be careful about the amount of silicon oil supplied in the oil bath.
Be sure that the amount of silicon oil supplied should be three liters or less.
Silicon oil has large thermal expansion and may overflow from the in-bath by heating.
Consider the amount of oil which may overflow by heating before supplying oil into the in-bath.
Ex): When using TSF485-50, the amount of oil supplied can be calculated with the following formula.
Oil increment = (preset temperature－current temperature) ×amount of oil ×0.00098
In case the preset temperature is 180℃, current temperature is 23℃, and amount of oil is 3.5ℓ, the
amount to be supplied is:
(180℃－23℃)×3.5×0.00098＝0.54L
In the above example, three liters of silicon oil is supplied.
Up to three liters
CAUTION!

11
2.Before Using This Unit
Preparations for Operation
Water/oil supply for in-bath
The in-bath installed on the main body is removable for easy supply of water/oil. Be careful about the
followings when supplying water/oil.
Water supply for BM model water bath
•Supply modest amount of water, considering overflow when sample flask is sunk into the bath.
•Wash the in-bath with water to keep it always clean. Remove the dirt on the in-bath, especially on
the bottom surface of interior where the heater or temperature sensor contacts, before setup.
•Wipe the water droplet on the outer surface of in-bath completely before setup. If it is installed on
the main body with water droplet remained, water splatter by heating of the heater or incorrect
temperature detection may result in.
•Do not place flammable substances onto the installation area of heater. A fire disaster may result
in.
•Clean the heater installation area frequently to keep it always clean. If not, malfunction of device
or fire disaster may result in.
•To clean in-bath, it was confirmed the bath not to so hot, turn off the power switch and remove the
power supply cord with plug.
Oil supply for BO model water bath
•The amount of oil to be supplied is three liters at maximum. Supply modest amount of oil,
considering overflow when sample flask is sunk into the bath.
•Wash the in-bath with mild detergent to keep it always clean. Remove the dirt on the in-bath,
especially on the bottom surface of interior where the heater or temperature sensor contacts, before
setup.
•Wipe the water droplet on the outer surface of in-bath completely and dry it before setup. If it is
installed on the main body with water droplet remained, water splatter by heating of the heater or
incorrect temperature detection may result in.
•Do not place flammable substances onto the installation area of heater. A fire disaster may result
in.
•Clean the heater installation area frequently to keep it always clean. If not, malfunction of device
or fire disaster may result in.
•To clean in-bath, it was confirmed the bath not to so hot, turn off the power switch and remove the
power supply cord with plug.
Handle with care.
Be careful about the amount of water/oil supplied.
Keep the bath and heater clean.
Do not spill fluid.

12
3.Description and Function of Each Part
Main Unit
Rear view
Front view Removable in-bath (SUS316)
Control panel
Connector for power cord
Outer covering
Made by heat-resistant
ABS resin
Exclusive connector for bath operational
setting function in rotary evaporator on
the RE600/800 model.
(The connecting cord is attached to the
RE600/800 model.)
Power switch (circuit breaker)

13
3.Description and Function of Each Part
Control Panel
No. Name Mark Function
①Preset temperature
/measured temperature
display screen
―
Usually displays bath temperature, and by key operation
displays character or preset temperature.
②HEATER lamp HEATER Lights up when heater is being operated.
③UP key ▲Increases the preset value.
④Down key ▼Decreases the preset value.
⑤START/STOP key START/STOP Starts/stops the operation of device by pressing it for one
minute.
⑥Operation lamp ―
Lights up during fixed temperature operation and blinks
during timer operation
⑦TIMER key TIMER Operation setting key for quick auto stop, auto stop and
auto start operation.
⑧MAINTENANCE key MAINTENANCE Goes into the MAINTENANCE menu by pressing the
TIMER key for a few seconds.
MAINTENANCE menu selection/setting key, including the
function of bath stop, heat-retention, key lock, calibration
offset, reparation at power failure and accumulated time
display.
⑨Exclusive connector for
operational setting
function
―
Connected to the rotary evaporator on the RE600/800
model and detects abnormality in bath stop, heat-retention
and bath temperature by instructions from RE main body
at the end of operation when bath stop and heat-retention
are selected with the MAINTENANCE key.
⑦
⑧
⑤
④
⑥
③
②
①
Exclusive connector for bath operational setting
function in rotary evaporator on the RE600/800
model.
(The connecting cord is attached to the
RE600/800 model.)
IN
OUT
LEAK
IN
OUT
LEAK
VR600/800
Vacuum controlle
r

14
3.Description and Function of Each Part
Characters of the Controller
Indicated characters for BM/BO type controller are follows;
Character Identifier Name Purpose
The characters on the timer selection screen
AStP
Selection/standby
screen display for quick
auto stop/auto stop
timer operation
Selection screen for quick auto stop timer
operation which stops the operation at preset time
and quick auto stop function.
AStr Selection/waiting
screen display for auto
start timer operation
Selection screen for auto start timer operation
which starts the operation at preset time.
The characters on the MAINTENANCE menu
LocK Keylock of preset value
Selection menu to keylock the operation to disable
the change of preset value.
On: keylock/Off: cancels keylock
bSEt Selection screen for
bath stop/heat-retention
Selection screen to switch the mode to stop the
bath automatically or to retain heat by the signals
from the RE main body at the completion of
operation. Only available when the RE600/800
model rotary evaporator is connected.
StoP Selection screen for
bath stop
Selection screen displayed when bath auto stop
mode is selected. Only available when the
RE600/800 model rotary evaporator is connected.
KEEP Selection screen for
bath heat-retention
Selection screen displayed when bath auto
heat-retention mode is selected. Only available
when the RE600/800 model rotary evaporator is
connected.
mnL Setting screen for bath
stop/heat-retention
(function disabling)
Selection screen displayed where the RE600/800
model rotary evaporator is not connected or bath
is used separately. This screen is set at factory
shipment.
Sv2 Setting screen for
heat-retention
temperature
Setting screen to set heat-retention temperature
of bath. Displayed when KEEP is selected in
bSet. Only available when the RE600/800 model
rotary evaporator is connected.
cAL Calibration offset
setting
Indicates that calibration offset temperature input
mode is selected.
Pon Selection screen for
reparation at power
failure
Selection screen to set the operational status of
device after power failure.
ON: recovers and continues operation.
OFF: remains operation stop state.
The setting is OFF at factory shipment.
* Also refer to Page 176 "Operation Mode, Function Setting Key, and Characters".

15
4.Operation Method
Operation Mode and Function List
The operation modes of this unit are as follows;
No. Name Description Page
1
Fixed Temperature
Operation
Set the desired temperature with the △▽ keys. Press the
START/STOP key for one second to start operation. Press the
same key again to stop operation.
187
2
Quick Auto Stop
Operation
Press the TIMER key during fixed temperature operation.
Select the and set the operating time with the △▽
keys. Press the START/STOP key for one second to start the
auto stop operation.
198
3
Auto Stop Operation Press the TIMER key during standby time before operation.
Select the and set the operating time with the △▽
keys. Press the START/STOP key for one second to start the
auto stop operation.
20
4
Auto Start Operation Press the TIMER key two times during standby time before
operation. Select the and set the operating time with
the △▽ keys. Press the START/STOP key for one second to
start the auto start operation.
232
The safety features of the device are described below;
No. Name Description Page
① Overheating prevention function:
This function is set to be automatically activated(manual
reset) when the temperature exceeds the setting
temperature by 40℃.
The “Er06” is displayed on the display screen when this
function operates. In this case, turn off the breaker and
call the service department.
The device recovers after the cause of problem is
removed and the circuit breaker is turned to on again.
1 Overheating prevention
device
② Thermal fuse:
The device contains a thermal fuse. The fuse works if the
overheating prevention function mentioned in the above
does not operate.
24
2 Circuit breaker The device has a power switch-type circuit breaker on the back
surface of main body. -

16
4.Operation Method
Operation Mode and Function List
The maintenance functions of device are described as follows.
The maintenance mode shares the operation key with the timer function. Keep pressing the TIMER key
for four seconds to go into the maintenance mode.
Name Description Page
1 Keylock function The function keylocks the preset temperature to disable its
change during operation. Select “on” or “oFF” with the △▽
key. “On” keylocks the preset value and “oFF” cancels the
keylock.
265
2 Bath operation setting function
(exclusive function available
only when the RE600/800
model rotary evaporator is
connected)
The function is available only when the RE600/800 model
rotary evaporator is connected. By interfacing with the
vacuum controller on the main body of rotary evaporator, the
function stops the bath automatically or keeps the bath in a
state of heat-retention when the rotary evaporator completes
the operation.
Press the TIMER key in the maintenance mode to display the
alternant display screen.
Select the with the △▽ keys to automatically stop
the bath when the rotary evaporator completes the operation.
Select the with the △▽ keys to keeps the bath in
a state of heat-retention when the rotary evaporator
completes the operation.
The setting at factory shipment is the mode to
disable the operation setting function.
Setting of heat-retention temperature
Select the and then press the TIMER key to set
the heat-retention temperature. Set the desired value with
the △▽ keys.
26
Calibration offset function The function corrects the temperature inside the bath by
adjusting it to the preset temperature in case the temperature
inside the bath does not reach or goes over the preset value.
This function can match the values of preset temperature and
temperature inside the bath.
The function can correct the value to either plus or minus side
within the whole thermal bandwidth of device.
Press the TIMER key to display the . Input the
correction value. The bath temperature increases when a
minus value is input. It decreases when a plus value is
input.
276
4 Reparation at power failure The function selects the operational state of bath at recovery
after power failure.
On: recovers and continues operation.
OFF: remains operation stop.
The setting at factory shipment is “OFF”.
Select the with the TIMER key and then select the
“on” or “oFF”with the △▽ keys.
287

17
4.Operation Method
Operation Mode, Function Setting Key, and Characters
The following key operations and characters are used for the settings of operation mode and functions.

18
4.Operation Method
Fixed Temperature Operation
Fix Temperature Operation is regular drive mode for continuous driving.
Fixed temperature
operation procedures 1. Turn on the power switch (turn the breaker to ON)
•After the power switch on the back surface of main body is
turned to on, the screen displays the initial values for about four
seconds. After that the screen goes into the standby state.
The indicator displays the current temperature inside the bath.
Refer to the P.14 for the characters of operation mode.
2. Set the temperature
•Set the desired temperature with the △▽ keys.
Press the △key or ▽key. The screen displays the preset
temperature. Press the △key to increase the value. Press
the ▽key to decrease the value.
After three seconds the screen displays the current bath
temperature.
CAUTION: When it adds some hot water while driven and the
liquid temperature is made 40℃or more higher than the preset
temperature, the device judges the temperature anomaly,
intercepts the heating circuit, and displays error 6.When it will add
some hot water, please cancel the drive.
3. Start operation
•Press the START/STOP key for about one second.
The device starts operation. The operation lamp lights up.
The HEATER lamp lights up and the temperature begin to
increase.
4. Stop operation
•Press the START/STOP key for about one second.
The device stops operation. The operation lamp lights off.
The HEATER lamp lights off.
The screen displays the current bath temperature.
To correct the setting mistake or check the preset value…
Press the △▽ key again to correct the setting mistake or to check the preset value.
The screen changes to the preset temperature screen to display it.
To change the preset temperature during operation…
Press the △▽ key during operation to change the preset temperature during operation. The device
goes into the setting mode where the preset temperature is possible to be changed. After the setting
with the △▽ keys, the device continues operation with the new preset temperature.
Screen for measured temperature/preset temperature:
The current temperature inside the bath is displayed without operation.