**5. Applications**

*Electrochemical Impedance Spectroscopy*

than other methods.

**other EDA recording systems**

correlated when lonely or separately measured.

ated with the psychophysiological state of the subject).

**4. Advantages of simultaneous measurement of SC, SP, and SS over** 

1.In order to make direct comparisons between different EDA recording methods or parameters, techniques for simultaneously recording EDA using the same skin site are required, since EDA responses cannot be compared and/or

2.Some authors such as [11] suggested a measuring method dependent on

continuously switching (sequentially) between AC (SC) and DC (SP) recording methods, which allows the same site to be used for recording both SC and SP. However, this recording method has drawback that the switching skin to a different EDA coupler will always result in an adaptation of the gain process, dependent on the filter characteristics of the amplifier system, which constitutes a time-consuming procedure. In addition, the subject will seat or stay for longer time in order to record EDA parameters one by one, which lead to nuisance of the subject, and may in turn affect EDA signals (as EDA is associ-

3.Also some other authors suggested another parallel-like (alternately) recordings of SC and SP measurements on contralateral sites [11]. But, this way of recording has disadvantage that the EDA parameters are not recorded at the same skin site. It has been pointed out that each active skin site may give rise to various types of EDA responses and that basic EDA levels all depend on the measuring system. So, measuring at the same electrode is significant because both EDA components (levels and response) are largely dependent on skin site as already mentioned above [47]. Besides the alternate method is inconvenient as both hands of the test subject are connected with the electrodes. In addition, to measure both SC and SP, at least four electrodes connected with two setups are required, which take economical cost. On the other hand, simultaneously employing only three electrodes that are placed on the same skin on a single hand makes it preferable and convenient where the subject will seat for shorter period than the other traditional recording methods. From an economic point of view, its cost is lower since one setup is used for recording all EDA parameters, and fewer electrodes are employed

4.Simultaneous method also has another important advantage over the rest of the methods, which could be achieved when AC exosomatic current method is used. Through this method in addition to SC and SP, the SS could be recorded simultaneously at the same skin site as well. This means that EDA measurements can be simultaneously appropriate with additional psychophysiological measures, as it may provide further insights into the sweat gland physiology, which makes it particularly useful for clinical applications. Technically based upon this method, voltage sensing is converted from analog to digital, and utilizing a low measuring frequency with phase-sensitive rectification guarantees genuinely constant voltage or current and enables the minimization of measurement errors as well. Moreover, this recording method enables detection of variations in the reference site potential, thereby checking to which extent the reference site is electrodermally inactive, which is a requirement for accurate SP recording. Therefore, it is very suitable for physiological

**106**

research.

The scope of applications will be primarily related to those studies recently conducted using the EDA measurement simultaneously. The use of simultaneous measurement of EDA in psychology, physiology, and medicine is widespread and constantly increasing due to its advantages. It is widely accepted that both AC and DC components (parameters) can be accurately measured.

Tronstad et al. [50] employed the system presented in Tronstad et al. [8], for the simultaneous recording of SC, SP, and SS at the same skin site. The aim of the study was to assess how accurately sweat production can be estimated based on combining the skin electrical properties. According to the authors, results of sweating estimation were significantly improved by the addition of SS and SP recordings to the SC recording only.

In a study [51], changes in SCR, SPR, and SSR were evaluated as a result of sequences of electrical (painful) stimuli with different intensities by using simultaneous system of EDA measurement. EDA responses as results of painful stimuli were recorded from 40 healthy volunteers. They reported that EDA responses significantly changed (increased) with respect to the intensity of the stimuli. Both SCR and SSR showed linear relationship with the painful stimuli. It was found that the EDA responses, particularly SCR (*p* < 0.001) and SSR (*p* = 0.001), were linearly affected by the intensity of the painful stimuli. Authors mentioned that EDA responses, in particular SCR, may be used as a useful indicator for assessment of experienced pain in clinical settings.

The same system mentioned above was used in another study [52], with the aim of exploring the influence of relative humidity on EDA levels and also the responses. A total of 10 healthy subjects were exposed to environments of low and high RH while EDA measures were recorded, including cognitive, visual, and breathing stimuli for evoking electrodermal responses of different origins. EDA levels and responses were compared between the two humidity levels for all stimuli and all EDA measures. It was found that EDA levels, in particular for SC and SS, were significantly increasing during high humidity exposure but that the change in EDA responses (SC, SS, and SP) was not statistically significant (*p* > 0.05, paired *t* test). Authors concluded that ambient humidity influences the recording of EDA levels and is important to consider when these parameters are used, but is not important in the recording or analysis of EDA responses.
