**3. EDA recording systems**

### **3.1 Sequentially recording SC and SP**

Some authors tried to measure EDA parameters at the same skin site, but such parameters were sequentially recorded.

Venables and Sayer [26] had determined the relationship between the SC and SP, by means of two measuring systems. The idea was to record both EDA parameters at the same skin (palm and inner surface of the left arm), but not simultaneously. They stated that due to the disturbance in the measurement of SP created by the

presence of the impressed voltage used to measure SC, the two measures were not taken simultaneously. It was found that the two measures are related, although not so highly as to make them equivalent [26].

The role of sweat gland activity in the mediation of SC and SP levels was investigated by Venables and Martin [27]. Both SP and SC were recorded at the same skin site (tips of the fore, middle, and ring fingers of each hand), but not simultaneously [27].

Turpin and Siddle [28] presented effects of series of auditory stimuli on the sequential SCR and SPR recordings. Bipolar recording of SC was accomplished by attaching electrodes on the medial phalanx of the index and second fingers of the non-preferred hand of the subject. Unipolar recording of SP was made by placing electrodes on the medial phalanx of the third finger of non-preferred as the active site, while the reference site was a point two thirds of the distance from the wrist to the elbow on the volar surface of the forearm [28].
